From: Jiri Olsa <jolsa@redhat.com>
To: "Jin, Yao" <yao.jin@linux.intel.com>
Cc: acme@kernel.org, jolsa@kernel.org, peterz@infradead.org,
mingo@redhat.com, alexander.shishkin@linux.intel.com,
Linux-kernel@vger.kernel.org, ak@linux.intel.com,
kan.liang@intel.com, yao.jin@intel.com
Subject: Re: [PATCH v1 2/2] perf header: Support hybrid CPU_PMU_CAPS
Date: Thu, 6 May 2021 15:22:35 +0200 [thread overview]
Message-ID: <YJPtmyzTEe/IUID4@krava> (raw)
In-Reply-To: <c0bd3baa-3209-23f3-7058-c6908434de2d@linux.intel.com>
On Thu, May 06, 2021 at 12:59:08PM +0800, Jin, Yao wrote:
> Hi Jiri,
>
> On 5/4/2021 11:07 PM, Jiri Olsa wrote:
> > On Fri, Apr 30, 2021 at 03:46:02PM +0800, Jin Yao wrote:
> > > On hybrid platform, it may have several cpu pmus, such as,
> > > "cpu_core" and "cpu_atom". The CPU_PMU_CAPS feature in perf
> > > header needs to be improved to support multiple cpu pmus.
> > >
> > > The new layout in header is defined as:
> > >
> > > <nr_caps>
> > > <caps string>
> > > <caps string>
> > > <pmu name>
> > > <nr of rest pmus>
> >
> > not sure why is the 'nr of rest pmus' needed
> >
>
> The 'nr of rest pmus' indicates the remaining pmus which are waiting for process.
>
> For example,
>
> <nr_caps>
> <caps string>
> "cpu_core"
> 1
> <nr_caps>
> <caps string>
> "cpu_atom"
> 0
>
> When we see '0' in data file processing, we know all the pmu have been processed yet.
>
> > the current format is:
> >
> > u32 nr_cpu_pmu_caps;
> > {
> > char name[];
> > char value[];
> > } [nr_cpu_pmu_caps]
> >
> >
> > I guess we could extend it to:
> >
> > u32 nr_cpu_pmu_caps;
> > {
> > char name[];
> > char value[];
> > } [nr_cpu_pmu_caps]
> > char pmu_name[]
> >
> > u32 nr_cpu_pmu_caps;
> > {
> > char name[];
> > char value[];
> > } [nr_cpu_pmu_caps]
> > char pmu_name[]
> >
> > ...
> >
> > and we could detect the old format by checking that there's no
> > pmu name.. but maybe I'm missing something, I did not check deeply,
> > please let me know
> >
>
> Actually we do the same thing, but I just add an extra 'nr of rest pmus'
> after the pmu_name. The purpose of 'nr of rest pmus' is when we see '0' at
> 'nr of rest pmus', we know that all pmus have been processed.
>
> Otherwise, we have to continue reading data file till we find something
> incorrect and then finally drop the last read data.
you have the size of the feature data right? I think we use
it in other cases to check if there are more data
>
> So is this solution acceptable?
>
> > also would be great to move the format change and storing hybrid
> > pmus in separate patches
> >
>
> Maybe we have to put the storing and processing into one patch.
>
> Say patch 1 contains the format change and storing hybrid pmus. And patch 2
> contains the processing for the new format. If the repo only contains the
> patch 1, I'm afraid that may introduce the compatible issue.
maybe you can have change of caps format in one patch
and storing/processing hybrid pmus in another?
jirka
next prev parent reply other threads:[~2021-05-06 13:22 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-30 7:46 [PATCH v1 1/2] perf header: Support HYBRID_TOPOLOGY feature Jin Yao
2021-04-30 7:46 ` [PATCH v1 2/2] perf header: Support hybrid CPU_PMU_CAPS Jin Yao
2021-05-04 15:07 ` Jiri Olsa
2021-05-06 4:59 ` Jin, Yao
2021-05-06 13:22 ` Jiri Olsa [this message]
2021-05-06 14:43 ` Jin, Yao
2021-05-10 13:11 ` Jiri Olsa
2021-05-11 1:15 ` Jin, Yao
2021-05-03 15:18 ` [PATCH v1 1/2] perf header: Support HYBRID_TOPOLOGY feature Arnaldo Carvalho de Melo
2021-05-04 2:03 ` Jin, Yao
2021-05-04 14:54 ` Jiri Olsa
2021-05-06 2:01 ` Jin, Yao
2021-05-04 14:56 ` Jiri Olsa
2021-05-04 19:28 ` Arnaldo Carvalho de Melo
2021-05-04 19:37 ` Jiri Olsa
2021-05-05 13:49 ` Arnaldo Carvalho de Melo
2021-05-05 20:28 ` Jiri Olsa
2021-05-06 2:22 ` Jin, Yao
2021-05-06 2:17 ` Jin, Yao
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