From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Andi Kleen <ak@linux.intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v14 0/3]: perf: reduce data loss when profiling highly parallel CPU bound workloads
Date: Thu, 25 Oct 2018 08:12:37 -0300 [thread overview]
Message-ID: <20181025111237.GA3782@kernel.org> (raw)
In-Reply-To: <20181025085439.GA4722@krava>
Em Thu, Oct 25, 2018 at 10:54:39AM +0200, Jiri Olsa escreveu:
> On Thu, Oct 25, 2018 at 10:59:36AM +0300, Alexey Budankov wrote:
> > Hi,
> >
> > On 15.10.2018 13:17, Jiri Olsa wrote:
> > > On Mon, Oct 15, 2018 at 09:26:09AM +0300, Alexey Budankov wrote:
> > >>
> > >> Currently in record mode the tool implements trace writing serially.
> > >> The algorithm loops over mapped per-cpu data buffers and stores
> > >> ready data chunks into a trace file using write() system call.
> > >>
> > >> At some circumstances the kernel may lack free space in a buffer
> > >> because the other buffer's half is not yet written to disk due to
> > >> some other buffer's data writing by the tool at the moment.
> > >>
> > >> Thus serial trace writing implementation may cause the kernel
> > >> to loose profiling data and that is what observed when profiling
> > >> highly parallel CPU bound workloads on machines with big number
> > >> of cores.
> > >>
> > >> Experiment with profiling matrix multiplication code executing 128
> > >> threads on Intel Xeon Phi (KNM) with 272 cores, like below,
> > >> demonstrates data loss metrics value of 98%:
> > >>
> > >> /usr/bin/time perf record -o /tmp/perf-ser.data -a -N -B -T -R -g \
> > >> --call-graph dwarf,1024 --user-regs=IP,SP,BP --switch-events \
> > >> -e cycles,instructions,ref-cycles,software/period=1,name=cs,config=0x3/Duk -- \
> > >> matrix.gcc
> > >
> > > I ran above on 24 cpu server and could not see the gain,
> > > but I guess I'd need much bigger server to see that
> > >
> > > anyway, the code is now nicely separated, and given the
> > > advertised results below I have no objections
> > >
> > > Reviewed-by: Jiri Olsa <jolsa@kernel.org>
> >
> > Is the plan Jiri mentioned earlier to have it as a stand alone patch kit
> > or upstream the changes into mainline?
>
> I haven't heard from Arnaldo yet, but I'd like to have this merged in
I'll try and go over it today.
- Arnaldo
prev parent reply other threads:[~2018-10-25 11:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-15 6:26 [PATCH v14 0/3]: perf: reduce data loss when profiling highly parallel CPU bound workloads Alexey Budankov
2018-10-15 6:42 ` [PATCH v14 1/3]: perf util: map data buffer for preserving collected data Alexey Budankov
2018-11-01 18:47 ` Song Liu
2018-11-02 16:14 ` Alexey Budankov
2018-10-15 6:44 ` [PATCH v14 2/3]: perf record: enable asynchronous trace writing Alexey Budankov
2018-11-01 18:42 ` Song Liu
2018-11-02 16:11 ` Alexey Budankov
2018-10-15 6:46 ` [PATCH v14 3/3]: perf record: extend trace writing to multi AIO Alexey Budankov
2018-11-01 18:30 ` Song Liu
2018-11-02 16:12 ` Alexey Budankov
2018-10-15 10:17 ` [PATCH v14 0/3]: perf: reduce data loss when profiling highly parallel CPU bound workloads Jiri Olsa
2018-10-25 7:59 ` Alexey Budankov
2018-10-25 8:54 ` Jiri Olsa
2018-10-25 11:12 ` Arnaldo Carvalho de Melo [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181025111237.GA3782@kernel.org \
--to=acme@kernel.org \
--cc=ak@linux.intel.com \
--cc=alexander.shishkin@linux.intel.com \
--cc=alexey.budankov@linux.intel.com \
--cc=jolsa@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.