linux-kernel - [PATCH 27/29] perf, x86: Add a Haswell precise instructions event v2

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Date:	Thu, 17 Jan 2013 12:36:50 -0800
From:	Andi Kleen <andi@...stfloor.org>
To:	mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	akpm@...ux-foundation.org, acme@...hat.com, eranian@...gle.com,
	jolsa@...hat.com, namhyung@...nel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 27/29] perf, x86: Add a Haswell precise instructions event v2

From: Andi Kleen <ak@...ux.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 <ak@...ux.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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