linux-kernel - Re: [PATCH v2] perf: disable PERF_RECORD

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Date:	Thu, 17 Oct 2013 09:54:09 -0600
From:	David Ahern <dsahern@...il.com>
To:	Stephane Eranian <eranian@...gle.com>, linux-kernel@...r.kernel.org
CC:	mingo@...e.hu, peterz@...radead.org, ak@...ux.intel.com,
	jolsa@...hat.com, acme@...hat.com, hughd@...gle.com
Subject: Re: [PATCH v2] perf: disable PERF_RECORD_MMAP2 support

On 10/17/13 8:28 AM, Stephane Eranian wrote:
>
> For now, we disable the extended MMAP record support (MMAP2).
> We have identified cases where it would not report the correct
> mapping information, clone(VM_CLONE) but with separate pids.
> We will revisit the support once we find a solution for this case.
>
> The patch changes the kernel to return EINVAL if attr->mmap2
> is set. The patch also modifies the perf tool to use regular PERF_RECORD_MMAP
> for synthetic events and it also prevents the tool from requesting attr->mmap2
> mode because the kernel would reject it.
>
> The support will be revisited once the kenrel interface is updated.

Why not disable mmap2 as well:

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 0ce9febf1ba0..289f34dbe970 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -678,7 +678,7 @@ void perf_evsel__config(struct perf_evsel *evsel,
         attr->sample_type   |= PERF_SAMPLE_WEIGHT;

     attr->mmap  = track;
-   attr->mmap2 = track && !perf_missing_features.mmap2;
+   /* attr->mmap2 = track && !perf_missing_features.mmap2; */
     attr->comm  = track;


David
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