[tip:perf/core] perf, x86: Improve the PEBS ABI

tip-bot for Peter Zijlstra
2010-05-07T18:44:44Z

Commit-ID: ab608344bcbde4f55ec4cd911b686b0ce3eae076
Gitweb: http://git.kernel.org/tip/ab608344bcbde4f55ec4cd911b686b0ce3eae076
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 8 Apr 2010 23:03:20 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 7 May 2010 11:31:02 +0200

perf, x86: Improve the PEBS ABI

Rename perf_event_attr::precise to perf_event_attr::precise_ip and
widen it to 2 bits. This new field describes the required precision of
the PERF_SAMPLE_IP field:

0 - SAMPLE_IP can have arbitrary skid
1 - SAMPLE_IP must have constant skid
2 - SAMPLE_IP requested to have 0 skid
3 - SAMPLE_IP must have 0 skid

And modify the Intel PEBS code accordingly. The PEBS implementation
now supports up to precise_ip == 2, where we perform the IP fixup.

Also s/PERF_RECORD_MISC_EXACT/&_IP/ to clarify its meaning, this bit
should be set for each PERF_SAMPLE_IP field known to match the actual
instruction triggering the event.

This new scheme allows for a PEBS mode that uses the buffer for more
than a single event.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/cpu/perf_event.c | 17 ++++++++++++++++-
arch/x86/kernel/cpu/perf_event_intel.c | 4 ++--
arch/x86/kernel/cpu/perf_event_intel_ds.c | 12 ++++++------
include/linux/perf_event.h | 23 +++++++++++++++++++----
tools/perf/builtin-top.c | 2 +-
tools/perf/util/parse-events.c | 25 ++++++++++++++++---------
6 files changed, 60 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 4a3f1f2..27fa9ee 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -488,6 +488,21 @@ static int x86_setup_perfctr(struct perf_event *event)

static int x86_pmu_hw_config(struct perf_event *event)
{
+ if (event->attr.precise_ip) {
+ int precise = 0;
+
+ /* Support for constant skid */
+ if (x86_pmu.pebs)
+ precise++;
+
+ /* Support for IP fixup */
+ if (x86_pmu.lbr_nr)
+ precise++;
+
+ if (event->attr.precise_ip > precise)
+ return -EOPNOTSUPP;
+ }
+
/*
* Generate PMC IRQs:
* (keep 'enabled' bit clear for now)
@@ -1780,7 +1795,7 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
}

if (regs->flags & PERF_EFLAGS_EXACT)
- misc |= PERF_RECORD_MISC_EXACT;
+ misc |= PERF_RECORD_MISC_EXACT_IP;

return misc;
}
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index a4b56ac..fdbc652 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -563,7 +563,7 @@ static void intel_pmu_disable_event(struct perf_event *event)

x86_pmu_disable_event(event);

- if (unlikely(event->attr.precise))
+ if (unlikely(event->attr.precise_ip))
intel_pmu_pebs_disable(event);
}

@@ -615,7 +615,7 @@ static void intel_pmu_enable_event(struct perf_event *event)
return;
}

- if (unlikely(event->attr.precise))
+ if (unlikely(event->attr.precise_ip))
intel_pmu_pebs_enable(event);

__x86_pmu_enable_event(hwc, ARCH_PERFMON_EVENTSEL_ENABLE);
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index 35056f7..18018d1 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -307,7 +307,7 @@ intel_pebs_constraints(struct perf_event *event)
{
struct event_constraint *c;

- if (!event->attr.precise)
+ if (!event->attr.precise_ip)
return NULL;

if (x86_pmu.pebs_constraints) {
@@ -330,7 +330,7 @@ static void intel_pmu_pebs_enable(struct perf_event *event)
cpuc->pebs_enabled |= 1ULL << hwc->idx;
WARN_ON_ONCE(cpuc->enabled);

- if (x86_pmu.intel_cap.pebs_trap)
+ if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1)
intel_pmu_lbr_enable(event);
}

@@ -345,7 +345,7 @@ static void intel_pmu_pebs_disable(struct perf_event *event)

hwc->config |= ARCH_PERFMON_EVENTSEL_INT;

- if (x86_pmu.intel_cap.pebs_trap)
+ if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1)
intel_pmu_lbr_disable(event);
}

@@ -485,7 +485,7 @@ static void __intel_pmu_pebs_event(struct perf_event *event,
regs.bp = pebs->bp;
regs.sp = pebs->sp;

- if (intel_pmu_pebs_fixup_ip(regs))
+ if (event->attr.precise_ip > 1 && intel_pmu_pebs_fixup_ip(&regs))
regs.flags |= PERF_EFLAGS_EXACT;
else
regs.flags &= ~PERF_EFLAGS_EXACT;
@@ -518,7 +518,7 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)

WARN_ON_ONCE(!event);

- if (!event->attr.precise)
+ if (!event->attr.precise_ip)
return;

n = top - at;
@@ -570,7 +570,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)

WARN_ON_ONCE(!event);

- if (!event->attr.precise)
+ if (!event->attr.precise_ip)
continue;

if (__test_and_set_bit(bit, (unsigned long *)&status))
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 6be4a0f..23cd005 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -203,9 +203,19 @@ struct perf_event_attr {
enable_on_exec : 1, /* next exec enables */
task : 1, /* trace fork/exit */
watermark : 1, /* wakeup_watermark */
- precise : 1, /* OoO invariant counter */
-
- __reserved_1 : 48;
+ /*
+ * precise_ip:
+ *
+ * 0 - SAMPLE_IP can have arbitrary skid
+ * 1 - SAMPLE_IP must have constant skid
+ * 2 - SAMPLE_IP requested to have 0 skid
+ * 3 - SAMPLE_IP must have 0 skid
+ *
+ * See also PERF_RECORD_MISC_EXACT_IP
+ */
+ precise_ip : 2, /* skid constraint */
+
+ __reserved_1 : 47;

union {
__u32 wakeup_events; /* wakeup every n events */
@@ -296,7 +306,12 @@ struct perf_event_mmap_page {
#define PERF_RECORD_MISC_GUEST_KERNEL (4 << 0)
#define PERF_RECORD_MISC_GUEST_USER (5 << 0)

-#define PERF_RECORD_MISC_EXACT (1 << 14)
+/*
+ * Indicates that the content of PERF_SAMPLE_IP points to
+ * the actual instruction that triggered the event. See also
+ * perf_event_attr::precise_ip.
+ */
+#define PERF_RECORD_MISC_EXACT_IP (1 << 14)
/*
* Reserve the last bit to indicate some extended misc field
*/
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 3de3977..ed9b5b6 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -1021,7 +1021,7 @@ static void event__process_sample(const event_t *self,
return;
}

- if (self->header.misc & PERF_RECORD_MISC_EXACT)
+ if (self->header.misc & PERF_RECORD_MISC_EXACT_IP)
exact_samples++;

if (event__preprocess_sample(self, session, &al, symbol_filter) < 0 ||
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index bc8b7e6..ae7f591 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -654,10 +654,6 @@ parse_raw_event(const char **strp, struct perf_event_attr *attr)
return EVT_FAILED;
n = hex2u64(str + 1, &config);
if (n > 0) {
- if (str[n+1] == 'p') {
- attr->precise = 1;
- n++;
- }
*strp = str + n + 1;
attr->type = PERF_TYPE_RAW;
attr->config = config;
@@ -692,19 +688,29 @@ static enum event_result
parse_event_modifier(const char **strp, struct perf_event_attr *attr)
{
const char *str = *strp;
- int eu = 1, ek = 1, eh = 1;
+ int exclude = 0;
+ int eu = 0, ek = 0, eh = 0, precise = 0;

if (*str++ != ':')
return 0;
while (*str) {
- if (*str == 'u')
+ if (*str == 'u') {
+ if (!exclude)
+ exclude = eu = ek = eh = 1;
eu = 0;
- else if (*str == 'k')
+ } else if (*str == 'k') {
+ if (!exclude)
+ exclude = eu = ek = eh = 1;
ek = 0;
- else if (*str == 'h')
+ } else if (*str == 'h') {
+ if (!exclude)
+ exclude = eu = ek = eh = 1;
eh = 0;
- else
+ } else if (*str == 'p') {
+ precise++;
+ } else
break;
+
++str;
}
if (str >= *strp + 2) {
@@ -712,6 +718,7 @@ parse_event_modifier(const char **strp, struct perf_event_attr *attr)
attr->exclude_user = eu;
attr->exclude_kernel = ek;
attr->exclude_hv = eh;
+ attr->precise_ip = precise;
return 1;
}
return 0;