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Document the invariants we maintain for the wait list of ww_mutexes.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-13-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Help catch cases where mutex_lock is used directly on w/w mutexes, which
otherwise result in the w/w tasks reading uninitialized data.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-12-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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optimistic spin
Lock stealing is less beneficial for w/w mutexes since we may just end up
backing off if we stole from a thread with an earlier acquire stamp that
already holds another w/w mutex that we also need. So don't spin
optimistically unless we are sure that there is no other waiter that might
cause us to back off.
Median timings taken of a contention-heavy GPU workload:
Before:
real 0m52.946s
user 0m7.272s
sys 1m55.964s
After:
real 0m53.086s
user 0m7.360s
sys 1m46.204s
This particular workload still spends 20%-25% of CPU in mutex_spin_on_owner
according to perf, but my attempts to further reduce this spinning based on
various heuristics all lead to an increase in measured wall time despite
the decrease in sys time.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-11-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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In the following scenario, thread #1 should back off its attempt to lock
ww1 and unlock ww2 (assuming the acquire context stamps are ordered
accordingly).
Thread #0 Thread #1
--------- ---------
successfully lock ww2
set ww1->base.owner
attempt to lock ww1
confirm ww1->ctx == NULL
enter mutex_spin_on_owner
set ww1->ctx
What was likely to happen previously is:
attempt to lock ww2
refuse to spin because
ww2->ctx != NULL
schedule()
detect thread #0 is off CPU
stop optimistic spin
return -EDEADLK
unlock ww2
wakeup thread #0
lock ww2
Now, we are more likely to see:
detect ww1->ctx != NULL
stop optimistic spin
return -EDEADLK
unlock ww2
successfully lock ww2
... because thread #1 will stop its optimistic spin as soon as possible.
The whole scenario is quite unlikely, since it requires thread #1 to get
between thread #0 setting the owner and setting the ctx. But since we're
idling here anyway, the additional check is basically free.
Found by inspection.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-10-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Instead of inlining __mutex_lock_common() 5 times, once for each
{state,ww} variant. Reduce this to two, ww and !ww.
Then add __always_inline to mutex_optimistic_spin(), so that that will
get inlined all 4 remaining times, for all {waiter,ww} variants.
text data bss dec hex filename
6301 0 0 6301 189d defconfig-build/kernel/locking/mutex.o
4053 0 0 4053 fd5 defconfig-build/kernel/locking/mutex.o
4257 0 0 4257 10a1 defconfig-build/kernel/locking/mutex.o
This reduces total text size and better separates the ww and !ww mutex
code generation.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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backoff when acquiring the lock
The wait list is sorted by stamp order, and the only waiting task that may
have to back off is the first waiter with a context.
The regular slow path does not have to wake any other tasks at all, since
all other waiters that would have to back off were either woken up when
the waiter was added to the list, or detected the condition before they
added themselves.
Median timings taken of a contention-heavy GPU workload:
Without this series:
real 0m59.900s
user 0m7.516s
sys 2m16.076s
With changes up to and including this patch:
real 0m52.946s
user 0m7.272s
sys 1m55.964s
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-9-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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wait list
While adding our task as a waiter, detect if another task should back off
because of us.
With this patch, we establish the invariant that the wait list contains
at most one (sleeping) waiter with ww_ctx->acquired > 0, and this waiter
will be the first waiter with a context.
Since only waiters with ww_ctx->acquired > 0 have to back off, this allows
us to be much more economical with wakeups.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-8-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Add regular waiters in stamp order. Keep adding waiters that have no
context in FIFO order and take care not to starve them.
While adding our task as a waiter, back off if we detect that there is
a waiter with a lower stamp in front of us.
Make sure to call lock_contended even when we back off early.
For w/w mutexes, being first in the wait list is only stable when
taking the lock without a context. Therefore, the purpose of the first
flag is split into two: 'first' remains to indicate whether we want to
spin optimistically, while 'handoff' indicates that we should be
prepared to accept a handoff.
For w/w locking with a context, we always accept handoffs after the
first schedule(), to handle the following sequence of events:
1. Task #0 unlocks and hands off to Task #2 which is first in line
2. Task #1 adds itself in front of Task #2
3. Task #2 wakes up and must accept the handoff even though it is no
longer first in line
Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <Nicolai.Haehnle@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-7-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Keep the documentation in the header file since there is no good place
for it in mutex.c: there are two rather different implementations with
different EXPORT_SYMBOLs for each function.
Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: =?UTF-8?q?Nicolai=20H=C3=A4hnle?= <Nicolai.Haehnle@amd.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-6-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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We will add a new field to struct mutex_waiter. This field must be
initialized for all waiters if any waiter uses the ww_use_ctx path.
So there is a trade-off: Keep ww_mutex locking without a context on
the faster non-use_ww_ctx path, at the cost of adding the
initialization to all mutex locks (including non-ww_mutexes), or avoid
the additional cost for non-ww_mutex locks, at the cost of adding
additional checks to the use_ww_ctx path.
We take the latter choice. It may be worth eliminating the users of
ww_mutex_lock(lock, NULL), but there are a lot of them.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-5-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The function will be re-used in subsequent patches.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-4-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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While reviewing the ww_mutex patches, I noticed that it was still
possible to (incorrectly) succeed for (incorrect) code like:
mutex_lock(&a);
mutex_lock(&a);
This was possible if the second mutex_lock() would block (as expected)
but then receive a spurious wakeup. At that point it would find itself
at the front of the queue, request a handoff and instantly claim
ownership and continue, since owner would point to itself.
Avoid this scenario and simplify the code by introducing a third low
bit to signal handoff pickup. So once we request handoff, unlock
clears the handoff bit and sets the pickup bit along with the new
owner.
This also removes the need for the .handoff argument to
__mutex_trylock(), since that becomes superfluous with PICKUP.
In order to guarantee enough low bits, ensure task_struct alignment is
at least L1_CACHE_BYTES (which seems a good ideal regardless).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 9d659ae14b54 ("locking/mutex: Add lock handoff to avoid starvation")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The use of any kind of wait queue is an overkill for pcpu-rwsems.
While one option would be to use the less heavy simple (swait)
flavor, this is still too much for what pcpu-rwsems needs. For one,
we do not care about any sort of queuing in that the only (rare) time
writers (and readers, for that matter) are queued is when trying to
acquire the regular contended rw_sem. There cannot be any further
queuing as writers are serialized by the rw_sem in the first place.
Given that percpu_down_write() must not be called after exit_notify(),
we can replace the bulky waitqueue with rcuwait such that a writer
can wait for its turn to take the lock. As such, we can avoid the
queue handling and locking overhead.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1484148146-14210-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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rcuwait provides support for (single) RCU-safe task wait/wake functionality,
with the caveat that it must not be called after exit_notify(), such that
we avoid racing with rcu delayed_put_task_struct callbacks, task_struct
being rcu unaware in this context -- for which we similarly have
task_rcu_dereference() magic, but with different return semantics, which
can conflict with the wakeup side.
The interfaces are quite straightforward:
rcuwait_wait_event()
rcuwait_wake_up()
More details are in the comments, but it's perhaps worth mentioning at least,
that users must provide proper serialization when waiting on a condition, and
avoid corrupting a concurrent waiter. Also care must be taken between the task
and the condition for when calling the wakeup -- we cannot miss wakeups. When
porting users, this is for example, a given when using waitqueues in that
everything is done under the q->lock. As such, it can remove sources of non
preemptable unbounded work for realtime.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1484148146-14210-2-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This is a nasty interface and setting the state of a foreign task must
not be done. As of the following commit:
be628be0956 ("bcache: Make gc wakeup sane, remove set_task_state()")
... everyone in the kernel calls set_task_state() with current, allowing
the helper to be removed.
However, as the comment indicates, it is still around for those archs
where computing current is more expensive than using a pointer, at least
in theory. An important arch that is affected is arm64, however this has
been addressed now [1] and performance is up to par making no difference
with either calls.
Of all the callers, if any, it's the locking bits that would care most
about this -- ie: we end up passing a tsk pointer to a lot of the lock
slowpath, and setting ->state on that. The following numbers are based
on two tests: a custom ad-hoc microbenchmark that just measures
latencies (for ~65 million calls) between get_task_state() vs
get_current_state().
Secondly for a higher overview, an unlink microbenchmark was used,
which pounds on a single file with open, close,unlink combos with
increasing thread counts (up to 4x ncpus). While the workload is quite
unrealistic, it does contend a lot on the inode mutex or now rwsem.
[1] https://lkml.kernel.org/r/1483468021-8237-1-git-send-email-mark.rutland@arm.com
== 1. x86-64 ==
Avg runtime set_task_state(): 601 msecs
Avg runtime set_current_state(): 552 msecs
vanilla dirty
Hmean unlink1-processes-2 36089.26 ( 0.00%) 38977.33 ( 8.00%)
Hmean unlink1-processes-5 28555.01 ( 0.00%) 29832.55 ( 4.28%)
Hmean unlink1-processes-8 37323.75 ( 0.00%) 44974.57 ( 20.50%)
Hmean unlink1-processes-12 43571.88 ( 0.00%) 44283.01 ( 1.63%)
Hmean unlink1-processes-21 34431.52 ( 0.00%) 38284.45 ( 11.19%)
Hmean unlink1-processes-30 34813.26 ( 0.00%) 37975.17 ( 9.08%)
Hmean unlink1-processes-48 37048.90 ( 0.00%) 39862.78 ( 7.59%)
Hmean unlink1-processes-79 35630.01 ( 0.00%) 36855.30 ( 3.44%)
Hmean unlink1-processes-110 36115.85 ( 0.00%) 39843.91 ( 10.32%)
Hmean unlink1-processes-141 32546.96 ( 0.00%) 35418.52 ( 8.82%)
Hmean unlink1-processes-172 34674.79 ( 0.00%) 36899.21 ( 6.42%)
Hmean unlink1-processes-203 37303.11 ( 0.00%) 36393.04 ( -2.44%)
Hmean unlink1-processes-224 35712.13 ( 0.00%) 36685.96 ( 2.73%)
== 2. ppc64le ==
Avg runtime set_task_state(): 938 msecs
Avg runtime set_current_state: 940 msecs
vanilla dirty
Hmean unlink1-processes-2 19269.19 ( 0.00%) 30704.50 ( 59.35%)
Hmean unlink1-processes-5 20106.15 ( 0.00%) 21804.15 ( 8.45%)
Hmean unlink1-processes-8 17496.97 ( 0.00%) 17243.28 ( -1.45%)
Hmean unlink1-processes-12 14224.15 ( 0.00%) 17240.21 ( 21.20%)
Hmean unlink1-processes-21 14155.66 ( 0.00%) 15681.23 ( 10.78%)
Hmean unlink1-processes-30 14450.70 ( 0.00%) 15995.83 ( 10.69%)
Hmean unlink1-processes-48 16945.57 ( 0.00%) 16370.42 ( -3.39%)
Hmean unlink1-processes-79 15788.39 ( 0.00%) 14639.27 ( -7.28%)
Hmean unlink1-processes-110 14268.48 ( 0.00%) 14377.40 ( 0.76%)
Hmean unlink1-processes-141 14023.65 ( 0.00%) 16271.69 ( 16.03%)
Hmean unlink1-processes-172 13417.62 ( 0.00%) 16067.55 ( 19.75%)
Hmean unlink1-processes-203 15293.08 ( 0.00%) 15440.40 ( 0.96%)
Hmean unlink1-processes-234 13719.32 ( 0.00%) 16190.74 ( 18.01%)
Hmean unlink1-processes-265 16400.97 ( 0.00%) 16115.22 ( -1.74%)
Hmean unlink1-processes-296 14388.60 ( 0.00%) 16216.13 ( 12.70%)
Hmean unlink1-processes-320 15771.85 ( 0.00%) 15905.96 ( 0.85%)
x86-64 (known to be fast for get_current()/this_cpu_read_stable() caching)
and ppc64 (with paca) show similar improvements in the unlink microbenches.
The small delta for ppc64 (2ms), does not represent the gains on the unlink
runs. In the case of x86, there was a decent amount of variation in the
latency runs, but always within a 20 to 50ms increase), ppc was more constant.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Cc: mark.rutland@arm.com
Link: http://lkml.kernel.org/r/1483479794-14013-5-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This patch effectively replaces the tsk pointer dereference
(which is obviously == current), to directly use get_current()
macro. This is to make the removal of setting foreign task
states smoother and painfully obvious. Performance win on some
archs such as x86-64 and ppc64. On a microbenchmark that calls
set_task_state() vs set_current_state() and an inode rwsem
pounding benchmark doing unlink:
== 1. x86-64 ==
Avg runtime set_task_state(): 601 msecs
Avg runtime set_current_state(): 552 msecs
vanilla dirty
Hmean unlink1-processes-2 36089.26 ( 0.00%) 38977.33 ( 8.00%)
Hmean unlink1-processes-5 28555.01 ( 0.00%) 29832.55 ( 4.28%)
Hmean unlink1-processes-8 37323.75 ( 0.00%) 44974.57 ( 20.50%)
Hmean unlink1-processes-12 43571.88 ( 0.00%) 44283.01 ( 1.63%)
Hmean unlink1-processes-21 34431.52 ( 0.00%) 38284.45 ( 11.19%)
Hmean unlink1-processes-30 34813.26 ( 0.00%) 37975.17 ( 9.08%)
Hmean unlink1-processes-48 37048.90 ( 0.00%) 39862.78 ( 7.59%)
Hmean unlink1-processes-79 35630.01 ( 0.00%) 36855.30 ( 3.44%)
Hmean unlink1-processes-110 36115.85 ( 0.00%) 39843.91 ( 10.32%)
Hmean unlink1-processes-141 32546.96 ( 0.00%) 35418.52 ( 8.82%)
Hmean unlink1-processes-172 34674.79 ( 0.00%) 36899.21 ( 6.42%)
Hmean unlink1-processes-203 37303.11 ( 0.00%) 36393.04 ( -2.44%)
Hmean unlink1-processes-224 35712.13 ( 0.00%) 36685.96 ( 2.73%)
== 2. ppc64le ==
Avg runtime set_task_state(): 938 msecs
Avg runtime set_current_state: 940 msecs
vanilla dirty
Hmean unlink1-processes-2 19269.19 ( 0.00%) 30704.50 ( 59.35%)
Hmean unlink1-processes-5 20106.15 ( 0.00%) 21804.15 ( 8.45%)
Hmean unlink1-processes-8 17496.97 ( 0.00%) 17243.28 ( -1.45%)
Hmean unlink1-processes-12 14224.15 ( 0.00%) 17240.21 ( 21.20%)
Hmean unlink1-processes-21 14155.66 ( 0.00%) 15681.23 ( 10.78%)
Hmean unlink1-processes-30 14450.70 ( 0.00%) 15995.83 ( 10.69%)
Hmean unlink1-processes-48 16945.57 ( 0.00%) 16370.42 ( -3.39%)
Hmean unlink1-processes-79 15788.39 ( 0.00%) 14639.27 ( -7.28%)
Hmean unlink1-processes-110 14268.48 ( 0.00%) 14377.40 ( 0.76%)
Hmean unlink1-processes-141 14023.65 ( 0.00%) 16271.69 ( 16.03%)
Hmean unlink1-processes-172 13417.62 ( 0.00%) 16067.55 ( 19.75%)
Hmean unlink1-processes-203 15293.08 ( 0.00%) 15440.40 ( 0.96%)
Hmean unlink1-processes-234 13719.32 ( 0.00%) 16190.74 ( 18.01%)
Hmean unlink1-processes-265 16400.97 ( 0.00%) 16115.22 ( -1.74%)
Hmean unlink1-processes-296 14388.60 ( 0.00%) 16216.13 ( 12.70%)
Hmean unlink1-processes-320 15771.85 ( 0.00%) 15905.96 ( 0.85%)
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Cc: mark.rutland@arm.com
Link: http://lkml.kernel.org/r/1483479794-14013-4-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
This patch effectively replaces the tsk pointer dereference
(which is obviously == current), to directly use get_current()
macro. This is to make the removal of setting foreign task
states smoother and painfully obvious. Performance win on some
archs such as x86-64 and ppc64 -- arm64 is no longer an issue.
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: mark.rutland@arm.com
Link: http://lkml.kernel.org/r/1483479794-14013-3-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
This patch effectively replaces the tsk pointer dereference (which is
obviously == current), to directly use get_current() macro. In this
case, do_exit() always passes current to exit_mm(), hence we can
simply get rid of the argument. This is also a performance win on some
archs such as x86-64 and ppc64 -- arm64 is no longer an issue.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Cc: mark.rutland@arm.com
Link: http://lkml.kernel.org/r/1483479794-14013-2-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
As Peter suggested [1] rejecting non sampling PEBS events,
because they dont make any sense and could cause bugs
in the NMI handler [2].
[1] http://lkml.kernel.org/r/20170103094059.GC3093@worktop
[2] http://lkml.kernel.org/r/1482931866-6018-3-git-send-email-jolsa@kernel.org
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vince@deater.net>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20170103142454.GA26251@krava
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
It's possible to set up PEBS events to get only errors and not
any data, like on SNB-X (model 45) and IVB-EP (model 62)
via 2 perf commands running simultaneously:
taskset -c 1 ./perf record -c 4 -e branches:pp -j any -C 10
This leads to a soft lock up, because the error path of the
intel_pmu_drain_pebs_nhm() does not account event->hw.interrupt
for error PEBS interrupts, so in case you're getting ONLY
errors you don't have a way to stop the event when it's over
the max_samples_per_tick limit:
NMI watchdog: BUG: soft lockup - CPU#22 stuck for 22s! [perf_fuzzer:5816]
...
RIP: 0010:[<ffffffff81159232>] [<ffffffff81159232>] smp_call_function_single+0xe2/0x140
...
Call Trace:
? trace_hardirqs_on_caller+0xf5/0x1b0
? perf_cgroup_attach+0x70/0x70
perf_install_in_context+0x199/0x1b0
? ctx_resched+0x90/0x90
SYSC_perf_event_open+0x641/0xf90
SyS_perf_event_open+0x9/0x10
do_syscall_64+0x6c/0x1f0
entry_SYSCALL64_slow_path+0x25/0x25
Add perf_event_account_interrupt() which does the interrupt
and frequency checks and call it from intel_pmu_drain_pebs_nhm()'s
error path.
We keep the pending_kill and pending_wakeup logic only in the
__perf_event_overflow() path, because they make sense only if
there's any data to deliver.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vince@deater.net>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1482931866-6018-2-git-send-email-jolsa@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Di Shen reported a race between two concurrent sys_perf_event_open()
calls where both try and move the same pre-existing software group
into a hardware context.
The problem is exactly that described in commit:
f63a8daa5812 ("perf: Fix event->ctx locking")
... where, while we wait for a ctx->mutex acquisition, the event->ctx
relation can have changed under us.
That very same commit failed to recognise sys_perf_event_context() as an
external access vector to the events and thereby didn't apply the
established locking rules correctly.
So while one sys_perf_event_open() call is stuck waiting on
mutex_lock_double(), the other (which owns said locks) moves the group
about. So by the time the former sys_perf_event_open() acquires the
locks, the context we've acquired is stale (and possibly dead).
Apply the established locking rules as per perf_event_ctx_lock_nested()
to the mutex_lock_double() for the 'move_group' case. This obviously means
we need to validate state after we acquire the locks.
Reported-by: Di Shen (Keen Lab)
Tested-by: John Dias <joaodias@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Min Chong <mchong@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: f63a8daa5812 ("perf: Fix event->ctx locking")
Link: http://lkml.kernel.org/r/20170106131444.GZ3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
There is problem with installing an event in a task that is 'stuck' on
an offline CPU.
Blocked tasks are not dis-assosciated from offlined CPUs, after all, a
blocked task doesn't run and doesn't require a CPU etc.. Only on
wakeup do we ammend the situation and place the task on a available
CPU.
If we hit such a task with perf_install_in_context() we'll loop until
either that task wakes up or the CPU comes back online, if the task
waking depends on the event being installed, we're stuck.
While looking into this issue, I also spotted another problem, if we
hit a task with perf_install_in_context() that is in the middle of
being migrated, that is we observe the old CPU before sending the IPI,
but run the IPI (on the old CPU) while the task is already running on
the new CPU, things also go sideways.
Rework things to rely on task_curr() -- outside of rq->lock -- which
is rather tricky. Imagine the following scenario where we're trying to
install the first event into our task 't':
CPU0 CPU1 CPU2
(current == t)
t->perf_event_ctxp[] = ctx;
smp_mb();
cpu = task_cpu(t);
switch(t, n);
migrate(t, 2);
switch(p, t);
ctx = t->perf_event_ctxp[]; // must not be NULL
smp_function_call(cpu, ..);
generic_exec_single()
func();
spin_lock(ctx->lock);
if (task_curr(t)) // false
add_event_to_ctx();
spin_unlock(ctx->lock);
perf_event_context_sched_in();
spin_lock(ctx->lock);
// sees event
So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'.
Because if CPU2's load of that variable were to observe NULL, it would
not try to schedule the ctx and we'd have a task running without its
counter, which would be 'bad'.
As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it
first and not see the event yet, then CPU0 must observe task_curr()
and retry. If the install happens first, then we must see the event on
sched-in and all is well.
I think we can translate the first part (until the 'must not be NULL')
of the scenario to a litmus test like:
C C-peterz
{
}
P0(int *x, int *y)
{
int r1;
WRITE_ONCE(*x, 1);
smp_mb();
r1 = READ_ONCE(*y);
}
P1(int *y, int *z)
{
WRITE_ONCE(*y, 1);
smp_store_release(z, 1);
}
P2(int *x, int *z)
{
int r1;
int r2;
r1 = smp_load_acquire(z);
smp_mb();
r2 = READ_ONCE(*x);
}
exists
(0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Where:
x is perf_event_ctxp[],
y is our tasks's CPU, and
z is our task being placed on the rq of CPU2.
The P0 smp_mb() is the one added by this patch, ordering the store to
perf_event_ctxp[] from find_get_context() and the load of task_cpu()
in task_function_call().
The smp_store_release/smp_load_acquire model the RCpc locking of the
rq->lock and the smp_mb() of P2 is the context switch switching from
whatever CPU2 was running to our task 't'.
This litmus test evaluates into:
Test C-peterz Allowed
States 7
0:r1=0; 2:r1=0; 2:r2=0;
0:r1=0; 2:r1=0; 2:r2=1;
0:r1=0; 2:r1=1; 2:r2=1;
0:r1=1; 2:r1=0; 2:r2=0;
0:r1=1; 2:r1=0; 2:r2=1;
0:r1=1; 2:r1=1; 2:r2=0;
0:r1=1; 2:r1=1; 2:r2=1;
No
Witnesses
Positive: 0 Negative: 7
Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Observation C-peterz Never 0 7
Hash=e427f41d9146b2a5445101d3e2fcaa34
And the strong and weak model agree.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Will Deacon <will.deacon@arm.com>
Cc: jeremy.linton@arm.com
Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y used to accumulate user time and
account it on ticks and context switches only through the
vtime_account_user() function.
Now this model has been generalized on the 3 archs for all kind of
cputime (system, irq, ...) and all the cputime flushing happens under
vtime_account_user().
So let's rename this function to better reflect its new role.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-11-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
The account_system_time() function is called with a cputime that
occurred while running in the kernel. The function detects which
context the CPU is currently running in and accounts the time to
the correct bucket. This forces the arch code to account the
cputime for hardirq and softirq immediately.
Such accounting function can be costly and perform unwelcome divisions
and multiplications, among others.
The arch code can delay the accounting for system time. For s390
the accounting is done once per timer tick and for each task switch.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
[ Rebase against latest linus tree and move account_system_index_scaled(). ]
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-10-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
Currently CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y accounts the cputime on
any context boundary: irq entry/exit, guest entry/exit, context switch,
etc...
Calling functions such as account_system_time(), account_user_time()
and such can be costly, especially if they are called on many fastpath
such as twice per IRQ. Those functions do more than just accounting to
kcpustat and task cputime. Depending on the config, some subsystems can
perform unpleasant multiplications and divisions, among other things.
So lets accumulate the cputime instead and delay the accounting on ticks
and context switches only.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-9-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
tick/task switch
Currently CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y accounts the cputime on
any context boundary: irq entry/exit, guest entry/exit, context switch,
etc...
Calling functions such as account_system_time(), account_user_time()
and such can be costly, especially if they are called on many fastpath
such as twice per IRQ. Those functions do more than just accounting to
kcpustat and task cputime. Depending on the config, some subsystems can
perform unpleasant multiplications and divisions, among other things.
So lets accumulate the cputime instead and delay the accounting on ticks
and context switches only.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-8-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
That in order to gather all cputime accumulation to the same place.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-7-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
In order to prepare for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y to delay
cputime accounting to the tick, provide finegrained accumulators to
powerpc in order to store the cputime until flushing.
While at it, normalize the name of several fields according to common
cputime naming.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-6-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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In order to prepare for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y to delay
cputime accounting to the tick, let's allow archs to account cputime
directly to gtime.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-5-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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In order to prepare for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE=y to delay
cputime accounting to the tick, let's provide APIs to account system
time to precise contexts: hardirq, softirq, pure system, ...
Inspired-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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On task switch we must initialize the current cputime of the next task
using the value of the previous task which got freshly updated.
But we are confusing that with doing the opposite, which should result
in incorrect cputime accounting.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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On context switch with powerpc32, the cputime is accumulated in the
thread_info struct. So the switching-in task must move forward its
start time snapshot to the current time in order to later compute the
delta spent in system mode.
This is what we do for the normal cputime by initializing the starttime
field to the value of the previous task's starttime which got freshly
updated.
But we are missing the update of the scaled cputime start time. As a
result we may be accounting too much scaled cputime later.
Fix this by initializing the scaled cputime the same way we do for
normal cputime.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1483636310-6557-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This is a follow-up of commit:
cfd8983f03c7b2 ("x86, locking/spinlocks: Remove ticket (spin)lock implementation")
The static_key structure 'paravirt_ticketlocks_enabled' is now removed as it is
no longer used.
As a result, the init functions kvm_spinlock_init_jump() and
xen_init_spinlocks_jump() are also removed.
A simple build and boot test was done to verify it.
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1484252878-1962-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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info->si_addr is of type void __user *, so it should be compared against
something from the same address space.
This fixes the following sparse error:
arch/x86/mm/mpx.c:296:27: error: incompatible types in comparison expression (different address spaces)
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The Intel Denverton microserver uses a 25 MHz TSC crystal,
so we can derive its exact [*] TSC frequency
using CPUID and some arithmetic, eg.:
TSC: 1800 MHz (25000000 Hz * 216 / 3 / 1000000)
[*] 'exact' is only as good as the crystal, which should be +/- 20ppm
Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/306899f94804aece6d8fa8b4223ede3b48dbb59c.1484287748.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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A UV4 chassis with only 2 sockets configured can unexpectedly
target the wrong UV hub. Fix the problem by limiting the minimum
size of a partition to 4 sockets even if only 2 are configured.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Russ Anderson <rja@hpe.com>
Acked-by: Dimitri Sivanich <sivanich@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170113152111.313888353@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Fix the panic where KEXEC'd kernel does not have access to EFI runtime
mappings. This may cause the extended UVsystab to not be available.
The solution is to revert to non-UV mode and continue with limited
capabilities.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Russ Anderson <rja@hpe.com>
Reviewed-by: Alex Thorlton <athorlton@sgi.com>
Acked-by: Dimitri Sivanich <sivanich@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170113152111.118886202@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Improve __kernel_text_address()/kernel_text_address() to return
true if the given address is on a kprobe's instruction slot
trampoline.
This can help stacktraces to determine the address is on a
text area or not.
To implement this atomically in is_kprobe_*_slot(), also change
the insn_cache page list to an RCU list.
This changes timings a bit (it delays page freeing to the RCU garbage
collection phase), but none of that is in the hot path.
Note: this change can add small overhead to stack unwinders because
it adds 2 additional checks to __kernel_text_address(). However, the
impact should be very small, because kprobe_insn_pages list has 1 entry
per 256 probes(on x86, on arm/arm64 it will be 1024 probes),
and kprobe_optinsn_pages has 1 entry per 32 probes(on x86).
In most use cases, the number of kprobe events may be less
than 20, which means that is_kprobe_*_slot() will check just one entry.
Tested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/148388747896.6869.6354262871751682264.stgit@devbox
[ Improved the changelog and coding style. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Intel Merrifield has legacy RTC in contrast to the rest on Intel MID
platforms.
Set legacy RTC flag explicitly in architecture initialization code and
allocate interrupt for it.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170113164355.66161-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Moorestown support was removed by commit:
1a8359e411eb ("x86/mid: Remove Intel Moorestown")
Remove this leftover.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: platform-driver-x86@vger.kernel.org
Link: http://lkml.kernel.org/r/20170112112331.93236-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs
Pull btrfs fixes from Chris Mason:
"These are all over the place.
The tracepoint part of the pull fixes a crash and adds a little more
information to two tracepoints, while the rest are good old fashioned
fixes"
* 'for-linus-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
btrfs: make tracepoint format strings more compact
Btrfs: add truncated_len for ordered extent tracepoints
Btrfs: add 'inode' for extent map tracepoint
btrfs: fix crash when tracepoint arguments are freed by wq callbacks
Btrfs: adjust outstanding_extents counter properly when dio write is split
Btrfs: fix lockdep warning about log_mutex
Btrfs: use down_read_nested to make lockdep silent
btrfs: fix locking when we put back a delayed ref that's too new
btrfs: fix error handling when run_delayed_extent_op fails
btrfs: return the actual error value from from btrfs_uuid_tree_iterate
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Pull ceph fixes from Ilya Dryomov:
"Two small fixups for the filesystem changes that went into this merge
window"
* tag 'ceph-for-4.10-rc4' of git://github.com/ceph/ceph-client:
ceph: fix get_oldest_context()
ceph: fix mds cluster availability check
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Pull VFIO fixes from Alex Williamson:
- Cleanups and bug fixes for the mtty sample driver (Dan Carpenter)
- Export and make use of has_capability() to fix incorrect use of
ns_capable() for testing task capabilities (Jike Song)
* tag 'vfio-v4.10-rc4' of git://github.com/awilliam/linux-vfio:
vfio/type1: Remove pid_namespace.h include
vfio iommu type1: fix the testing of capability for remote task
capability: export has_capability
vfio-mdev: remove some dead code
vfio-mdev: buffer overflow in ioctl()
vfio-mdev: return -EFAULT if copy_to_user() fails
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Pull KVM fixes from Paolo Bonzini:
- fix for module unload vs deferred jump labels (note: there might be
other buggy modules!)
- two NULL pointer dereferences from syzkaller
- also syzkaller: fix emulation of fxsave/fxrstor/sgdt/sidt, problem
made worse during this merge window, "just" kernel memory leak on
releases
- fix emulation of "mov ss" - somewhat serious on AMD, less so on Intel
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
KVM: x86: fix emulation of "MOV SS, null selector"
KVM: x86: fix NULL deref in vcpu_scan_ioapic
KVM: eventfd: fix NULL deref irqbypass consumer
KVM: x86: Introduce segmented_write_std
KVM: x86: flush pending lapic jump label updates on module unload
jump_labels: API for flushing deferred jump label updates
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 fixes from Catalin Marinas:
- Fix huge_ptep_set_access_flags() to return "changed" when any of the
ptes in the contiguous range is changed, not just the last one
- Fix the adr_l assembly macro to work in modules under KASLR
* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
arm64: assembler: make adr_l work in modules under KASLR
arm64: hugetlb: fix the wrong return value for huge_ptep_set_access_flags
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Discard can return -EIO asynchronously if the alignment for the request
isn't suitable for the driver, which makes a proper fallback to other
methods in __blkdev_issue_zeroout impossible. Thus only issue a sync
discard from blkdev_issue_zeroout an don't try discard at all from
__blkdev_issue_zeroout as a non-invasive workaround.
One more reason why abusing discard for zeroing must die..
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Eryu Guan <eguan@redhat.com>
Fixes: e73c23ff ("block: add async variant of blkdev_issue_zeroout")
Signed-off-by: Jens Axboe <axboe@fb.com>
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Now that we have the blk_rq_payload_bytes helper available to determine
the actual I/O size we don't need to mess around with __data_len for
WRITE SAME.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
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The new blk_rq_payload_bytes generalizes the payload length hacks
that nvme_map_len did before.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
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Without that we'll pass a wrong payload size in cmd->sdb, which
can lead to hangs with drivers that need the total transfer size.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Chris Valean <v-chvale@microsoft.com>
Reported-by: Dexuan Cui <decui@microsoft.com>
Fixes: f9d03f96 ("block: improve handling of the magic discard payload")
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>
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Add a helper to calculate the actual data transfer size for special
payload requests.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
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