From: "Paul A. Clarke" <pc@us.ibm.com>
To: Ian Rogers <irogers@google.com>
Cc: Andi Kleen <ak@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>, Kajol Jain <kjain@linux.ibm.com>,
John Garry <john.garry@huawei.com>,
Jin Yao <yao.jin@linux.intel.com>,
Kan Liang <kan.liang@linux.intel.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
Kim Phillips <kim.phillips@amd.com>,
LKML <linux-kernel@vger.kernel.org>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
linux-perf-users <linux-perf-users@vger.kernel.org>,
Stephane Eranian <eranian@google.com>
Subject: Re: [RFC PATCH 0/7] Share events between metrics
Date: Tue, 15 Dec 2020 09:08:12 -0600 [thread overview]
Message-ID: <20201215150812.GA38786@li-24c3614c-2adc-11b2-a85c-85f334518bdb.ibm.com> (raw)
In-Reply-To: <CAP-5=fV2eNAt0LLHYXeLMR6GZi_oGZyzz8psErNkbahLQs-VLQ@mail.gmail.com>
On Thu, May 07, 2020 at 10:43:43PM -0700, Ian Rogers wrote:
> On Thu, May 7, 2020 at 2:47 PM Andi Kleen <ak@linux.intel.com> wrote:
> >
> > > > - without this change events within a metric may get scheduled
> > > > together, after they may appear as part of a larger group and be
> > > > multiplexed at different times, lowering accuracy - however, less
> > > > multiplexing may compensate for this.
Does mutiplexing somewhat related events at different times actually reduce
accuracy, or is it just more likely to give that appearance?
It seems that perf measurements are only useful if the workload is in a
fairly steady state. If there is some wobbling, then measuring at the
same time is more accurate for the periods where the events are being
measured simultaneously, but may be far off for when they are not being
measured at all. Spreading them out over a longer duration may actually
increase accuracy by sampling over more varied intervals.
Or, is the concern more about trying to time-slice the results in a
fairly granular way and expecting accurate results then?
(Or, maybe my ignorance is showing again. :-)
PC
next prev parent reply other threads:[~2020-12-15 15:09 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-07 8:14 [RFC PATCH 0/7] Share events between metrics Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 1/7] perf expr: migrate expr ids table to libbpf's hashmap Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 2/7] perf metricgroup: change evlist_used to a bitmap Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 3/7] perf metricgroup: free metric_events on error Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 4/7] perf metricgroup: always place duration_time last Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 5/7] perf metricgroup: delay events string creation Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 6/7] perf metricgroup: order event groups by size Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 8:14 ` [RFC PATCH 7/7] perf metricgroup: remove duped metric group events Ian Rogers
2020-05-07 8:14 ` Ian Rogers
2020-05-07 13:49 ` [RFC PATCH 0/7] Share events between metrics Jiri Olsa
2020-05-07 13:49 ` Jiri Olsa
2020-05-07 14:11 ` Ian Rogers
2020-05-07 14:11 ` Ian Rogers
2020-05-07 17:48 ` Andi Kleen
2020-05-07 17:48 ` Andi Kleen
2020-05-07 18:15 ` Ian Rogers
2020-05-07 18:15 ` Ian Rogers
2020-05-07 21:46 ` Andi Kleen
2020-05-07 21:46 ` Andi Kleen
2020-05-08 5:43 ` Ian Rogers
2020-05-08 5:43 ` Ian Rogers
2020-12-15 15:08 ` Paul A. Clarke [this message]
2020-12-15 18:39 ` Andi Kleen
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