From: Andi Kleen <a...@linux.intel.com>
Add a instructions-p event alias that uses the PDIR randomized instruction
retirement event. This is useful to avoid some systematic sampling shadow
problems. Normally PEBS sampling has a systematic shadow. With PDIR
enabled the hardware adds some randomization that statistically avoids
this problem. In this sense, it's more precise over a whole sampling
interval, but an individual sample can be less precise. But since we
sample overall it's a more precise event.
This could be used before using the explicit event code syntax, but it's easier
and more user friendly to use with an "instructions-p" alias. I expect
this will eventually become a common use case.
Right now for Haswell, will add to Ivy Bridge later too.
v2: Use new sysfs infrastructure
Signed-off-by: Andi Kleen <a...@linux.intel.com>
---
arch/x86/kernel/cpu/perf_event_intel.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c
b/arch/x86/kernel/cpu/perf_event_intel.c
index 022246a..fa20a19 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2027,6 +2027,7 @@ EVENT_ATTR_STR(cycles-t, cycles_t,
"event=0x3c,intx=1");
EVENT_ATTR_STR(cycles-ct, cycles_ct, "event=0x3c,intx=1,intx_cp=1");
EVENT_ATTR_STR(instructions-t, instructions_t, "event=0xc0,intx=1");
EVENT_ATTR_STR(instructions-ct,instructions_ct,"event=0xc0,intx=1,intx_cp=1");
+EVENT_ATTR_STR(instructions-p, instructions_p,
"event=0xc0,umask=0x01,precise=2");
static struct attribute *hsw_events_attrs[] = {
EVENT_PTR(tx_start),
@@ -2047,6 +2048,7 @@ static struct attribute *hsw_events_attrs[] = {
EVENT_PTR(cycles_ct),
EVENT_PTR(instructions_t),
EVENT_PTR(instructions_ct),
+ EVENT_PTR(instructions_p),
NULL
};
--
1.7.7.6
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