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authorLinus Torvalds <torvalds@linux-foundation.org>2016-03-24 10:02:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-03-24 10:02:14 -0700
commit3fa2fe2ce09c5a16be69c5319eb3347271a99735 (patch)
tree7067760e7006dec7ac6fe18fe3d09851293b63ea /kernel/events
parentd88f48e12821ab4b2244124d50ac094568f48db5 (diff)
parent05f5ece76a88a2cd4859bc93f90379733dd8b4a3 (diff)
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar: "This tree contains various perf fixes on the kernel side, plus three hw/event-enablement late additions: - Intel Memory Bandwidth Monitoring events and handling - the AMD Accumulated Power Mechanism reporting facility - more IOMMU events ... and a final round of perf tooling updates/fixes" * 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits) perf llvm: Use strerror_r instead of the thread unsafe strerror one perf llvm: Use realpath to canonicalize paths perf tools: Unexport some methods unused outside strbuf.c perf probe: No need to use formatting strbuf method perf help: Use asprintf instead of adhoc equivalents perf tools: Remove unused perf_pathdup, xstrdup functions perf tools: Do not include stringify.h from the kernel sources tools include: Copy linux/stringify.h from the kernel tools lib traceevent: Remove redundant CPU output perf tools: Remove needless 'extern' from function prototypes perf tools: Simplify die() mechanism perf tools: Remove unused DIE_IF macro perf script: Remove lots of unused arguments perf thread: Rename perf_event__preprocess_sample_addr to thread__resolve perf machine: Rename perf_event__preprocess_sample to machine__resolve perf tools: Add cpumode to struct perf_sample perf tests: Forward the perf_sample in the dwarf unwind test perf tools: Remove misplaced __maybe_unused perf list: Fix documentation of :ppp perf bench numa: Fix assertion for nodes bitfield ...
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c114
-rw-r--r--kernel/events/ring_buffer.c6
2 files changed, 82 insertions, 38 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 712570dddacd..de24fbce5277 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -376,8 +376,11 @@ static void update_perf_cpu_limits(void)
u64 tmp = perf_sample_period_ns;
tmp *= sysctl_perf_cpu_time_max_percent;
- do_div(tmp, 100);
- ACCESS_ONCE(perf_sample_allowed_ns) = tmp;
+ tmp = div_u64(tmp, 100);
+ if (!tmp)
+ tmp = 1;
+
+ WRITE_ONCE(perf_sample_allowed_ns, tmp);
}
static int perf_rotate_context(struct perf_cpu_context *cpuctx);
@@ -409,7 +412,13 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
if (ret || !write)
return ret;
- update_perf_cpu_limits();
+ if (sysctl_perf_cpu_time_max_percent == 100) {
+ printk(KERN_WARNING
+ "perf: Dynamic interrupt throttling disabled, can hang your system!\n");
+ WRITE_ONCE(perf_sample_allowed_ns, 0);
+ } else {
+ update_perf_cpu_limits();
+ }
return 0;
}
@@ -423,62 +432,68 @@ int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
#define NR_ACCUMULATED_SAMPLES 128
static DEFINE_PER_CPU(u64, running_sample_length);
+static u64 __report_avg;
+static u64 __report_allowed;
+
static void perf_duration_warn(struct irq_work *w)
{
- u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);
- u64 avg_local_sample_len;
- u64 local_samples_len;
-
- local_samples_len = __this_cpu_read(running_sample_length);
- avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;
-
printk_ratelimited(KERN_WARNING
- "perf interrupt took too long (%lld > %lld), lowering "
- "kernel.perf_event_max_sample_rate to %d\n",
- avg_local_sample_len, allowed_ns >> 1,
- sysctl_perf_event_sample_rate);
+ "perf: interrupt took too long (%lld > %lld), lowering "
+ "kernel.perf_event_max_sample_rate to %d\n",
+ __report_avg, __report_allowed,
+ sysctl_perf_event_sample_rate);
}
static DEFINE_IRQ_WORK(perf_duration_work, perf_duration_warn);
void perf_sample_event_took(u64 sample_len_ns)
{
- u64 allowed_ns = ACCESS_ONCE(perf_sample_allowed_ns);
- u64 avg_local_sample_len;
- u64 local_samples_len;
+ u64 max_len = READ_ONCE(perf_sample_allowed_ns);
+ u64 running_len;
+ u64 avg_len;
+ u32 max;
- if (allowed_ns == 0)
+ if (max_len == 0)
return;
- /* decay the counter by 1 average sample */
- local_samples_len = __this_cpu_read(running_sample_length);
- local_samples_len -= local_samples_len/NR_ACCUMULATED_SAMPLES;
- local_samples_len += sample_len_ns;
- __this_cpu_write(running_sample_length, local_samples_len);
+ /* Decay the counter by 1 average sample. */
+ running_len = __this_cpu_read(running_sample_length);
+ running_len -= running_len/NR_ACCUMULATED_SAMPLES;
+ running_len += sample_len_ns;
+ __this_cpu_write(running_sample_length, running_len);
/*
- * note: this will be biased artifically low until we have
- * seen NR_ACCUMULATED_SAMPLES. Doing it this way keeps us
+ * Note: this will be biased artifically low until we have
+ * seen NR_ACCUMULATED_SAMPLES. Doing it this way keeps us
* from having to maintain a count.
*/
- avg_local_sample_len = local_samples_len/NR_ACCUMULATED_SAMPLES;
-
- if (avg_local_sample_len <= allowed_ns)
+ avg_len = running_len/NR_ACCUMULATED_SAMPLES;
+ if (avg_len <= max_len)
return;
- if (max_samples_per_tick <= 1)
- return;
+ __report_avg = avg_len;
+ __report_allowed = max_len;
- max_samples_per_tick = DIV_ROUND_UP(max_samples_per_tick, 2);
- sysctl_perf_event_sample_rate = max_samples_per_tick * HZ;
- perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
+ /*
+ * Compute a throttle threshold 25% below the current duration.
+ */
+ avg_len += avg_len / 4;
+ max = (TICK_NSEC / 100) * sysctl_perf_cpu_time_max_percent;
+ if (avg_len < max)
+ max /= (u32)avg_len;
+ else
+ max = 1;
- update_perf_cpu_limits();
+ WRITE_ONCE(perf_sample_allowed_ns, avg_len);
+ WRITE_ONCE(max_samples_per_tick, max);
+
+ sysctl_perf_event_sample_rate = max * HZ;
+ perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
if (!irq_work_queue(&perf_duration_work)) {
- early_printk("perf interrupt took too long (%lld > %lld), lowering "
+ early_printk("perf: interrupt took too long (%lld > %lld), lowering "
"kernel.perf_event_max_sample_rate to %d\n",
- avg_local_sample_len, allowed_ns >> 1,
+ __report_avg, __report_allowed,
sysctl_perf_event_sample_rate);
}
}
@@ -4210,6 +4225,14 @@ static void __perf_event_period(struct perf_event *event,
active = (event->state == PERF_EVENT_STATE_ACTIVE);
if (active) {
perf_pmu_disable(ctx->pmu);
+ /*
+ * We could be throttled; unthrottle now to avoid the tick
+ * trying to unthrottle while we already re-started the event.
+ */
+ if (event->hw.interrupts == MAX_INTERRUPTS) {
+ event->hw.interrupts = 0;
+ perf_log_throttle(event, 1);
+ }
event->pmu->stop(event, PERF_EF_UPDATE);
}
@@ -9426,10 +9449,29 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
+ /*
+ * This must be done before the CPU comes alive, because the
+ * moment we can run tasks we can encounter (software) events.
+ *
+ * Specifically, someone can have inherited events on kthreadd
+ * or a pre-existing worker thread that gets re-bound.
+ */
perf_event_init_cpu(cpu);
break;
case CPU_DOWN_PREPARE:
+ /*
+ * This must be done before the CPU dies because after that an
+ * active event might want to IPI the CPU and that'll not work
+ * so great for dead CPUs.
+ *
+ * XXX smp_call_function_single() return -ENXIO without a warn
+ * so we could possibly deal with this.
+ *
+ * This is safe against new events arriving because
+ * sys_perf_event_open() serializes against hotplug using
+ * get_online_cpus().
+ */
perf_event_exit_cpu(cpu);
break;
default:
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 1faad2cfdb9e..c61f0cbd308b 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -746,8 +746,10 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
rb->user_page = all_buf;
rb->data_pages[0] = all_buf + PAGE_SIZE;
- rb->page_order = ilog2(nr_pages);
- rb->nr_pages = !!nr_pages;
+ if (nr_pages) {
+ rb->nr_pages = 1;
+ rb->page_order = ilog2(nr_pages);
+ }
ring_buffer_init(rb, watermark, flags);