linux-kernel - Re: [tip:perf/core] perf record: Add record.build-id config option

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Date:	Fri, 8 Jan 2016 17:58:50 +0900
From:	Taeung Song <treeze.taeung@...il.com>
To:	namhyung@...nel.org
Cc:	acme@...hat.com, jolsa@...nel.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, treeze.taeung@...il.com
Subject: Re: [tip:perf/core] perf record: Add record.build-id config option


Hi, Namhyung

I found accidentally a missing thing on Documentation/perf-record.txt.
A trifling thing..

On 12/18/2015 05:51 PM, tip-bot for Namhyung Kim wrote:
> Commit-ID:  7a29c087ff80f5d534bd6729c852099fc572c8d0
> Gitweb:     http://git.kernel.org/tip/7a29c087ff80f5d534bd6729c852099fc572c8d0
> Author:     Namhyung Kim <namhyung@...nel.org>
> AuthorDate: Tue, 15 Dec 2015 10:49:56 +0900
> Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
> CommitDate: Tue, 15 Dec 2015 11:46:16 -0300
>
> perf record: Add record.build-id config option
>
> Post processing at 'perf record' takes a long time on big machines.
>
> What it does is to find the build-id of binaries found in the event
> stream, so that it can make sure, at 'report' time, that the symtabs (be
> it ELF, kallsyms, etc) being used to resolve symbols are the ones
> matching the binaries found at 'record' time.
>
> Sometimes we just want to skip this processing of events at the end of
> the session to get quicker results, making sure the binaries haven't
> changed from 'record' to 'report' time.
>
> Add a new config option to control this behavior.
>
> The record.build-id config variable can have one of the following
> values:
>
>   - cache: post-process data and save/update the binaries into the
>            build-id cache (in ~/.debug).  This is the default.
>   - no-cache: post-process the data but not update the build-id cache.
>               Same effect as using the -N option.
>   - skip: skip post-processing and do not update the cache.
>           Same effect as using the -B option.
>
> Reported-and-Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> Acked-by: Jiri Olsa <jolsa@...nel.org>
> Cc: David Ahern <dsahern@...il.com>
> Cc: Taeung Song <treeze.taeung@...il.com>
> Link: http://lkml.kernel.org/r/1450144196-22957-1-git-send-email-namhyung@kernel.org
> [ Added some more text to the documentation ]
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>   tools/perf/Documentation/perf-record.txt | 14 +++++++++++++-
>   tools/perf/builtin-record.c              | 13 +++++++++++++
>   2 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index 8d032f4..3a1a32f 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -207,11 +207,23 @@ comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-
>   In per-thread mode with inheritance mode on (default), samples are captured only when
>   the thread executes on the designated CPUs. Default is to monitor all CPUs.
>
> +-B::
> +--no-buildid::
> +Do not save the build ids of binaries in the perf.data files. This skips
> +post processing after recording, which sometimes makes the final step in
> +the recording process to take a long time, as it needs to process all
> +events looking for mmap records. The downside is that it can misresolve
> +symbols if the workload binaries used when recording get locally rebuilt
> +or upgraded, because the only key available in this case is the
> +pathname. You can also set the "record.build-id" config variable to
> +'skip to have this behaviour permanently.

The 'skip' needs to be surrounded by single quotes.
A single quote is missing.

Thanks,
Taeung

> +
>   -N::
>   --no-buildid-cache::
>   Do not update the buildid cache. This saves some overhead in situations
>   where the information in the perf.data file (which includes buildids)
> -is sufficient.
> +is sufficient.  You can also set the "record.build-id" config variable to
> +'no-cache' to have the same effect.
>
>   -G name,...::
>   --cgroup name,...::
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 3ef3c79..a3b4930 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -837,6 +837,19 @@ int record_callchain_opt(const struct option *opt,
>
>   static int perf_record_config(const char *var, const char *value, void *cb)
>   {
> +	struct record *rec = cb;
> +
> +	if (!strcmp(var, "record.build-id")) {
> +		if (!strcmp(value, "cache"))
> +			rec->no_buildid_cache = false;
> +		else if (!strcmp(value, "no-cache"))
> +			rec->no_buildid_cache = true;
> +		else if (!strcmp(value, "skip"))
> +			rec->no_buildid = true;
> +		else
> +			return -1;
> +		return 0;
> +	}
>   	if (!strcmp(var, "record.call-graph"))
>   		var = "call-graph.record-mode"; /* fall-through */
>
>