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Message-Id: <1406016602-31845-7-git-send-email-zheng.z.yan@intel.com>
Date: Tue, 22 Jul 2014 16:09:59 +0800
From: "Yan, Zheng" <zheng.z.yan@...el.com>
To: linux-kernel@...r.kernel.org
Cc: a.p.zijlstra@...llo.nl, mingo@...nel.org, acme@...radead.org,
eranian@...gle.com, andi@...stfloor.org,
"Yan, Zheng" <zheng.z.yan@...el.com>
Subject: [PATCH v3 6/9] perf, x86: handle multiple records in PEBS buffer
When PEBS interrupt threshold is larger than one, the PEBS buffer
may include mutiple records for each PEBS event. This patch makes
the code first count how many records each PEBS event has, then
output the samples in batch.
One corner case needs to mention is that the PEBS hardware doesn't
deal well with collisions, when PEBS events happen near to each
other. The records for the events can be collapsed into a single
one. However in practice collisions are extremely rare, as long as
different events are used. The periods are typically very large,
so any collision is unlikely. When collision happens, we can either
drop the PEBS record or use the record to serve multiple events.
This patch chooses the later approach.
Signed-off-by: Yan, Zheng <zheng.z.yan@...el.com>
---
arch/x86/kernel/cpu/perf_event_intel_ds.c | 88 +++++++++++++++++++++----------
1 file changed, 59 insertions(+), 29 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index 86ef5b0..1e3b8cf 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -989,18 +989,51 @@ static void setup_pebs_sample_data(struct perf_event *event,
}
static void __intel_pmu_pebs_event(struct perf_event *event,
- struct pt_regs *iregs, void *__pebs)
+ struct pt_regs *iregs,
+ void *at, void *top, int count)
{
+ struct perf_output_handle handle;
+ struct perf_event_header header;
struct perf_sample_data data;
struct pt_regs regs;
- if (!intel_pmu_save_and_restart(event))
+ if (!intel_pmu_save_and_restart(event) &&
+ !(event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD))
return;
- setup_pebs_sample_data(event, iregs, __pebs, &data, ®s);
+ setup_pebs_sample_data(event, iregs, at, &data, ®s);
- if (perf_event_overflow(event, &data, ®s))
+ if (perf_event_overflow(event, &data, ®s)) {
x86_pmu_stop(event, 0);
+ return;
+ }
+
+ if (count <= 1)
+ return;
+
+ at += x86_pmu.pebs_record_size;
+ count--;
+
+ perf_sample_data_init(&data, 0, event->hw.last_period);
+ perf_prepare_sample(&header, &data, event, ®s);
+
+ if (perf_output_begin(&handle, event, header.size * count))
+ return;
+
+ for (; at < top; at += x86_pmu.pebs_record_size) {
+ struct pebs_record_nhm *p = at;
+ if (!(p->status & (1 << event->hw.idx)))
+ continue;
+
+ setup_pebs_sample_data(event, iregs, at, &data, ®s);
+ perf_output_sample(&handle, &header, &data, event);
+
+ count--;
+ if (count == 0)
+ break;
+ }
+
+ perf_output_end(&handle);
}
static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
@@ -1041,61 +1074,58 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
WARN_ONCE(n > 1, "bad leftover pebs %d\n", n);
at += n - 1;
- __intel_pmu_pebs_event(event, iregs, at);
+ __intel_pmu_pebs_event(event, iregs, at, top, 1);
}
static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
{
struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
struct debug_store *ds = cpuc->ds;
- struct perf_event *event = NULL;
- void *at, *top;
- u64 status = 0;
+ struct perf_event *event;
+ void *base, *at, *top;
int bit;
+ int counts[MAX_PEBS_EVENTS] = {};
if (!x86_pmu.pebs_active)
return;
- at = (struct pebs_record_nhm *)(unsigned long)ds->pebs_buffer_base;
+ base = (struct pebs_record_nhm *)(unsigned long)ds->pebs_buffer_base;
top = (struct pebs_record_nhm *)(unsigned long)ds->pebs_index;
ds->pebs_index = ds->pebs_buffer_base;
- if (unlikely(at > top))
+ if (unlikely(base >= top))
return;
- /*
- * Should not happen, we program the threshold at 1 and do not
- * set a reset value.
- */
- WARN_ONCE(top - at > x86_pmu.max_pebs_events * x86_pmu.pebs_record_size,
- "Unexpected number of pebs records %ld\n",
- (long)(top - at) / x86_pmu.pebs_record_size);
-
- for (; at < top; at += x86_pmu.pebs_record_size) {
+ for (at = base; at < top; at += x86_pmu.pebs_record_size) {
struct pebs_record_nhm *p = at;
-
+ /*
+ * PEBS creates only one entry if multiple counters
+ * overflow simultaneously.
+ */
for_each_set_bit(bit, (unsigned long *)&p->status,
x86_pmu.max_pebs_events) {
event = cpuc->events[bit];
if (!test_bit(bit, cpuc->active_mask))
continue;
-
WARN_ON_ONCE(!event);
-
if (!event->attr.precise_ip)
continue;
-
- if (__test_and_set_bit(bit, (unsigned long *)&status))
- continue;
-
- break;
+ counts[bit]++;
}
+ }
- if (!event || bit >= x86_pmu.max_pebs_events)
+ for (bit = 0; bit < MAX_PEBS_EVENTS; bit++) {
+ if (counts[bit] == 0)
continue;
+ event = cpuc->events[bit];
+ for (at = base; at < top; at += x86_pmu.pebs_record_size) {
+ struct pebs_record_nhm *p = at;
+ if (p->status & (1 << bit))
+ break;
+ }
- __intel_pmu_pebs_event(event, iregs, at);
+ __intel_pmu_pebs_event(event, iregs, at, top, counts[bit]);
}
}
--
1.9.3
--
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