linux-kernel - [PATCH] perf: make the breakpoint events sample period default to 1

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Date:	Sat, 14 Jul 2012 19:40:09 +0800
From:	Jovi Zhang <bookjovi@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] perf: make the breakpoint events sample period default to 1

>From cb06e8f21d3875f4ffef46a7627dca88b2c74836 Mon Sep 17 00:00:00 2001
From: Jovi Zhang <bookjovi@...il.com>
Date: Sun, 15 Jul 2012 03:03:10 +0800
Subject: [PATCH] perf: make the breakpoint events sample period default to 1

There have one problem about hw_breakpoint perf event, as watched,
the events reported to userspace is not correctly, sometime one
trigger bp_event report several events, sometime bp_event cannot
go through to user.

The root cause is attr->freq is 1 passed to kernel defaultly in
bp events, this make kernel calculate event period not as expect,
make sample period to 1 will change attr->freq to 0, to fix this problem.

This patch is similar with commit f92128 about tracepoint events:
    perf: Make the trace events sample period default to 1

Signed-off-by: Jovi Zhang <bookjovi@...il.com>
---
 tools/perf/util/parse-events.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 05dbc8b..631aec6 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -592,6 +592,7 @@ int parse_events_add_breakpoint(struct list_head
**list, int *idx,
 		attr.bp_len = HW_BREAKPOINT_LEN_4;

 	attr.type = PERF_TYPE_BREAKPOINT;
+	attr.sample_period = 1;

 	snprintf(name, MAX_NAME_LEN, "mem:%p:%s", ptr, type ? type : "rw");
 	return add_event(list, idx, &attr, name);
-- 
1.7.9.7
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