linux-kernel - Re: [RFC/PATCH 00/14] perf record: Add support to store data in directory

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Date:   Mon, 11 Feb 2019 21:18:31 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Stephane Eranian <eranian@...gle.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [RFC/PATCH 00/14] perf record: Add support to store data in
 directory

On Mon, Feb 11, 2019 at 04:32:02PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Mon, Feb 11, 2019 at 07:53:06PM +0100, Jiri Olsa escreveu:
> > On Mon, Feb 11, 2019 at 10:34:16AM -0800, Stephane Eranian wrote:
> > > On Mon, Feb 11, 2019 at 2:20 AM Jiri Olsa <jolsa@...hat.com> wrote:
> > > > On Tue, Feb 05, 2019 at 02:37:27PM +0100, Jiri Olsa wrote:
> > > > I think all could be added and worked around with exception
> > > > of BUILD_ID, which we store at the end (after processing
> > > > all data) and we need it early in the report phase
> 
> > > Buildids are injected after the fact via perf inject when in pipe mode.
> 
> > > > maybe it's time to re-think that buildid -> mmap event
> > > > association again, because it's pain in current implementation
> > > > as well
> 
> > > Sure, but what do you propose?
> 
> > this:
> > 
> > > > looks like bpf code is actualy getting build ids and storing
> > > > it for the callchains in kernel.. we can check if we can do
> > > > something similar for mmap events
> 
> kernel/bpf/stackmap.c
> 
> /* Parse build ID from 64-bit ELF */
> static int stack_map_get_build_id_64(void *page_addr,
>                                      unsigned char *build_id)
> 
> yeah, wasn't aware of that, good thing doing backports, huh? :-)
> 
> So do you thing about having a PERF_SAMPLE_BUILDID in sample_type and go
> and stash that thing in PERF_RECORD_MMAP2?

I thought having new MMAP3 event version with buildid field in it
if available and/or enabled by bit in perf_event_attr

jirka