From: Jiri Olsa <jolsa@redhat.com>
To: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Jiri Olsa <jolsa@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Namhyung Kim <namhyung@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Michael Petlan <mpetlan@redhat.com>,
Song Liu <songliubraving@fb.com>,
"Frank Ch. Eigler" <fche@redhat.com>,
Ian Rogers <irogers@google.com>,
Alexey Budankov <alexey.budankov@linux.intel.com>,
Andi Kleen <ak@linux.intel.com>,
Adrian Hunter <adrian.hunter@intel.com>
Subject: Re: [PATCH 02/26] perf: Introduce mmap3 version of mmap event
Date: Mon, 14 Sep 2020 21:56:04 +0200 [thread overview]
Message-ID: <20200914195604.GR1714160@krava> (raw)
In-Reply-To: <CABPqkBSKpZFbYWrQueS9cFDkGJPb3NdA1HTPh0+XN_+qvLpdLw@mail.gmail.com>
On Mon, Sep 14, 2020 at 10:26:05AM -0700, Stephane Eranian wrote:
> On Mon, Sep 14, 2020 at 2:08 AM <peterz@infradead.org> wrote:
> >
> > On Sun, Sep 13, 2020 at 11:41:00PM -0700, Stephane Eranian wrote:
> > > On Sun, Sep 13, 2020 at 2:03 PM Jiri Olsa <jolsa@kernel.org> wrote:
> > > what happens if I set mmap3 and mmap2?
> > >
> > > I think using mmap3 for every mmap may be overkill as you add useless
> > > 20 bytes to an mmap record.
> > > I am not sure if your code handles the case where mmap3 is not needed
> > > because there is no buildid, e.g, anonymous memory.
> > > It seems to me you've written the patch in such a way that if the user
> > > tool supports mmap3, then it supersedes mmap2, and thus
> > > you need all the fields of mmap2. But if could be more interesting to
> > > return either MMAP2 or MMAP3 depending on tool support
> > > and type of mmap, that would certainly save 20 bytes on any anon mmap.
> > > But maybe that logic is already in your patch and I missed it.
> >
> > That, and what if you don't want any of that buildid nonsense at all? I
> > always kill that because it makes perf pointlessly slow and has
> > absolutely no upsides for me.
> >
> I have seen situations where the perf tool takes a visibly significant
> amount of time (many seconds) to inject the buildids at the end of the
> collection
> of perf record (same if using perf inject -b). That is because it
> needs to go through all the records in the perf.data to find MMAP
> records and then read
> the buildids from the filesystem. This has caused some problems in our
> environment. Having the kernel add the buildid to *relevant* mmaps
> would avoid
> a lot of that penalty, by avoiding having to parse the perf.data file
> and leveraging the fact that the buildid may be in memory already.
> Although my concern on
> this has to do with large pages and the impact they have on alignment
> of sections in memory. I think Ian can comment better on this.
>
> I think this patch series is useful if it can demonstrate a speedup
> during recording (perf record or perf record | perf inject -b). But it
I haven't meassured, but I assume skipping of perf.data search
at the end of the record will make up for reading buildid for
each mmap event.. migt be tricky in mmap events heavy workloads
> needs to be
> optimized to minimize the volume of useless info returned. And Jiri
> needs to decide if MMAP3 is a replacement of MMAP2, or a different
> kind of record
> targeted at ELF images only in which case some of the fields may be
> removed. My tendency would be to go for the latter.
yes, I like the latter as well, let's see
thanks,
jirka
next prev parent reply other threads:[~2020-09-14 19:56 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-13 21:02 [RFC 00/26] perf: Add mmap3 support Jiri Olsa
2020-09-13 21:02 ` [PATCH 01/26] bpf: Move stack_map_get_build_id into lib Jiri Olsa
2020-09-14 6:09 ` Song Liu
2020-09-13 21:02 ` [PATCH 02/26] perf: Introduce mmap3 version of mmap event Jiri Olsa
2020-09-14 5:38 ` Namhyung Kim
2020-09-14 6:20 ` Song Liu
2020-09-14 19:38 ` Jiri Olsa
2020-09-14 15:28 ` Arnaldo Carvalho de Melo
2020-09-14 16:35 ` peterz
2020-09-14 17:08 ` Ian Rogers
2020-09-14 20:07 ` Jiri Olsa
2020-09-15 5:49 ` Adrian Hunter
2020-09-14 19:38 ` Jiri Olsa
2020-09-14 19:39 ` Jiri Olsa
2020-09-14 22:00 ` Arnaldo Carvalho de Melo
2020-09-15 5:39 ` Adrian Hunter
2020-09-14 19:38 ` Jiri Olsa
2020-09-15 2:54 ` Namhyung Kim
2020-09-14 6:41 ` Stephane Eranian
2020-09-14 9:08 ` peterz
2020-09-14 15:32 ` Arnaldo Carvalho de Melo
2020-09-14 17:26 ` Stephane Eranian
2020-09-14 19:56 ` Jiri Olsa [this message]
2020-09-15 0:03 ` Ian Rogers
2020-09-14 15:31 ` Arnaldo Carvalho de Melo
2020-09-14 19:50 ` Jiri Olsa
2020-09-14 22:38 ` Arnaldo Carvalho de Melo
2020-09-14 19:45 ` Jiri Olsa
2020-09-14 9:36 ` peterz
2020-09-13 21:02 ` [PATCH 03/26] tools headers uapi: Sync tools/include/uapi/linux/perf_event.h Jiri Olsa
2020-09-14 5:39 ` Namhyung Kim
2020-09-13 21:02 ` [PATCH 04/26] perf tools: Add filename__decompress function Jiri Olsa
2020-09-14 15:35 ` Arnaldo Carvalho de Melo
2020-09-14 20:43 ` Jiri Olsa
2020-09-17 18:54 ` Arnaldo Carvalho de Melo
2020-09-18 10:51 ` Jiri Olsa
2020-09-13 21:02 ` [PATCH 05/26] perf tools: Add build_id__is_defined function Jiri Olsa
2020-09-14 5:44 ` Namhyung Kim
2020-09-14 16:03 ` Arnaldo Carvalho de Melo
2020-09-14 20:49 ` Jiri Olsa
2020-09-14 20:47 ` Jiri Olsa
2020-09-14 21:51 ` Arnaldo Carvalho de Melo
2020-09-13 21:02 ` [PATCH 06/26] perf tools: Add support to read build id from compressed elf Jiri Olsa
2020-09-14 16:04 ` Arnaldo Carvalho de Melo
2020-09-14 20:49 ` Jiri Olsa
2020-09-13 21:02 ` [PATCH 07/26] perf tools: Add check for existing link in buildid dir Jiri Olsa
2020-09-14 5:54 ` Namhyung Kim
2020-09-14 20:18 ` Jiri Olsa
2020-09-13 21:02 ` [PATCH 08/26] perf tools: Use struct extra_kernel_map in machine__process_kernel_mmap_event Jiri Olsa
2020-09-13 21:02 ` [PATCH 09/26] perf tools: Try load vmlinux from buildid database Jiri Olsa
2020-09-14 6:25 ` Namhyung Kim
2020-09-14 20:29 ` Jiri Olsa
2020-09-15 2:58 ` Namhyung Kim
2020-09-13 21:02 ` [PATCH 10/26] perf tools: Enable mmap3 map event when supported Jiri Olsa
2020-09-14 16:05 ` Arnaldo Carvalho de Melo
2020-09-13 21:02 ` [PATCH 11/26] perf tools: Add mmap3 support Jiri Olsa
2020-09-13 21:02 ` [PATCH 12/26] perf tools: Set build id for kernel dso objects Jiri Olsa
2020-09-13 21:03 ` [PATCH 13/26] perf tools: Plug in mmap3 event Jiri Olsa
2020-09-13 21:03 ` [PATCH 14/26] perf tools: Add mmap3 events to --show-mmap-events option Jiri Olsa
2020-09-14 6:30 ` Namhyung Kim
2020-09-14 20:29 ` Jiri Olsa
2020-09-13 21:03 ` [PATCH 15/26] perf tools: Synthesize proc tasks with mmap3 Jiri Olsa
2020-09-14 16:07 ` Arnaldo Carvalho de Melo
2020-09-14 20:51 ` Jiri Olsa
2020-09-13 21:03 ` [PATCH 16/26] perf tools: Synthesize modules " Jiri Olsa
2020-09-14 16:07 ` Arnaldo Carvalho de Melo
2020-09-15 20:17 ` Ian Rogers
2020-09-16 8:20 ` Jiri Olsa
2020-09-16 14:07 ` Arnaldo Carvalho de Melo
2020-09-16 14:17 ` peterz
2020-09-16 15:10 ` Arnaldo Carvalho de Melo
2020-09-16 15:20 ` peterz
2020-09-16 15:21 ` Jiri Olsa
2020-09-16 15:42 ` Arnaldo Carvalho de Melo
2020-09-13 21:03 ` [PATCH 17/26] perf tools: Synthesize kernel " Jiri Olsa
2020-09-14 16:08 ` Arnaldo Carvalho de Melo
2020-09-13 21:03 ` [PATCH 18/26] perf tests: Add mmap3 support for perf record test Jiri Olsa
2020-09-13 21:03 ` [PATCH 19/26] perf tools: Add buildid-list support for mmap3 Jiri Olsa
2020-09-13 21:03 ` [PATCH 20/26] perf tools: Add build_id_cache__add function Jiri Olsa
2020-09-14 16:13 ` Arnaldo Carvalho de Melo
2020-09-13 21:03 ` [PATCH 21/26] perf tools: Add machine__for_each_dso function Jiri Olsa
2020-09-14 16:15 ` Arnaldo Carvalho de Melo
2020-09-13 21:03 ` [PATCH 22/26] perf tools: Use machine__for_each_dso in perf_session__cache_build_ids Jiri Olsa
2020-09-13 21:03 ` [PATCH 23/26] perf tools: Add __perf_session__cache_build_ids function Jiri Olsa
2020-09-13 21:03 ` [PATCH 24/26] perf tools: Add buildid-list --store option Jiri Olsa
2020-09-14 6:42 ` Namhyung Kim
2020-09-14 15:14 ` Arnaldo Carvalho de Melo
2020-09-14 20:42 ` Jiri Olsa
2020-09-14 20:42 ` Jiri Olsa
2020-09-13 21:03 ` [PATCH 25/26] perf tools: Move debuginfo download code into get_debuginfo Jiri Olsa
2020-09-13 21:03 ` [PATCH 26/26] perf tools: Add report --store option Jiri Olsa
2020-09-14 5:25 ` [RFC 00/26] perf: Add mmap3 support Namhyung Kim
2020-09-14 15:13 ` Arnaldo Carvalho de Melo
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