summaryrefslogtreecommitdiff
path: root/kernel/events
diff options
context:
space:
mode:
authorAlexander Shishkin <alexander.shishkin@linux.intel.com>2015-01-14 14:18:13 +0200
committerIngo Molnar <mingo@kernel.org>2015-04-02 17:14:10 +0200
commit6a279230391b63130070e0219b0ad09d34d28c89 (patch)
tree0acce118e036a8474a77fde1c899819580478ab6 /kernel/events
parent0a4e38e64f5e91ce131cc42ee5bb3925377ec840 (diff)
perf: Add a capability for AUX_NO_SG pmus to do software double buffering
For pmus that don't support scatter-gather for AUX data in hardware, it might still make sense to implement software double buffering to avoid losing data while the user is reading data out. For this purpose, add a pmu capability that guarantees multiple high-order chunks for AUX buffer, so that the pmu driver can do switchover tricks. To make use of this feature, add PERF_PMU_CAP_AUX_SW_DOUBLEBUF to your pmu's capability mask. This will make the ring buffer AUX allocation code ensure that the biggest high order allocation for the aux buffer pages is no bigger than half of the total requested buffer size, thus making sure that the buffer has at least two high order allocations. Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kaixu Xia <kaixu.xia@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Robert Richter <rric@kernel.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: acme@infradead.org Cc: adrian.hunter@intel.com Cc: kan.liang@intel.com Cc: markus.t.metzger@intel.com Cc: mathieu.poirier@linaro.org Link: http://lkml.kernel.org/r/1421237903-181015-5-git-send-email-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/ring_buffer.c15
1 files changed, 14 insertions, 1 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index ed0859e33b2f..6e3be7a10c50 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -287,13 +287,26 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
if (!has_aux(event))
return -ENOTSUPP;
- if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG)
+ if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
/*
* We need to start with the max_order that fits in nr_pages,
* not the other way around, hence ilog2() and not get_order.
*/
max_order = ilog2(nr_pages);
+ /*
+ * PMU requests more than one contiguous chunks of memory
+ * for SW double buffering
+ */
+ if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_SW_DOUBLEBUF) &&
+ !overwrite) {
+ if (!max_order)
+ return -EINVAL;
+
+ max_order--;
+ }
+ }
+
rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
if (!rb->aux_pages)
return -ENOMEM;