From: Namhyung Kim <namhyung@kernel.org>
To: "Liang, Kan" <kan.liang@intel.com>
Cc: "acme@kernel.org" <acme@kernel.org>,
"jolsa@kernel.org" <jolsa@kernel.org>,
"ak@linux.intel.com" <ak@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Hunter, Adrian" <adrian.hunter@intel.com>
Subject: Re: [PATCH RFC V3 3/5] perf,tool: partial time support
Date: Tue, 14 Jul 2015 10:04:49 +0900 [thread overview]
Message-ID: <20150714010449.GB16880@danjae.kornet> (raw)
In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F0770188BEF4@SHSMSX103.ccr.corp.intel.com>
On Mon, Jul 13, 2015 at 07:01:51PM +0000, Liang, Kan wrote:
> > On Wed, Jul 08, 2015 at 04:44:55AM -0400, kan.liang@intel.com wrote:
> > > From: Kan Liang <kan.liang@intel.com>
> > >
> > > When multiple events are sampled it may not be needed to collect fine
> > > grained time stamps on all events. The sample sites are usually nearby.
> > > It's enough to have time stamps on the regular reference events.
> > > This patchkit adds the ability to turn off time stamps per event. This
> > > in term can reduce sampling overhead and the size of the perf.data.
> >
> > So this patch makes the PERF_SAMPLE_TIME bit set or not independently,
> > right? But AFAIK we sometimes just use first evsel for checking
> > sample_type value, especially for evlist->id_pos. I'm not sure it'll work for
> > all cases of mixed time/notime events..
> >
>
> If the sample_type is different, IDENTIFIER will be set to make sure id is in
> a fixed position. So we don't need to worry about evlist->id_pos here.
>
> I think the only unsupported case should be that the kernel doesn't
> support IDENTIFIER. If so, under my test, perf record will print warning
> " failed to process type". Perf report will also print warning
> " non matching sample_type". So the user can switch back to full time
> support.
Ah, ok then.
> If you think the warning is not good enough, we can show specific
> warning and error out when non IDENTIFIER support is detected.
Well, I think it's good enough. :)
However, perf_evlist__id_hdr_size() seems to be affected also. Are
you sure it's okay too?
Thanks,
Namhyung
next prev parent reply other threads:[~2015-07-14 1:07 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-08 8:44 [PATCH RFC V3 0/5] partial callgrap and time support kan.liang
2015-07-08 8:44 ` [PATCH RFC V3 1/5] perf,tools: introduce OPT_CALLBACK_SET/OPT_CALLBACK_NOOPT_SET kan.liang
2015-07-14 6:54 ` Jiri Olsa
2015-07-08 8:44 ` [PATCH RFC V3 2/5] perf/documentation: Add description for period kan.liang
2015-07-14 6:55 ` Jiri Olsa
2015-07-14 14:05 ` Arnaldo Carvalho de Melo
2015-07-21 9:31 ` [tip:perf/core] perf record: Document setting '-e pmu/period=N/' in man page tip-bot for Kan Liang
2015-07-08 8:44 ` [PATCH RFC V3 3/5] perf,tool: partial time support kan.liang
2015-07-13 13:27 ` Namhyung Kim
2015-07-13 19:01 ` Liang, Kan
2015-07-14 1:04 ` Namhyung Kim [this message]
2015-07-15 19:03 ` Liang, Kan
2015-07-17 7:12 ` Namhyung Kim
2015-07-14 6:54 ` Jiri Olsa
2015-07-14 6:54 ` Jiri Olsa
2015-07-08 8:44 ` [PATCH RFC V3 4/5] perf,tool: partial callgrap support kan.liang
2015-07-08 8:44 ` [PATCH RFC V3 5/5] perf,tests: Add tests to callgrap and time parse kan.liang
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