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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: Mon, 10 May 2021 15:11:44 +0200	[thread overview]
Message-ID: <YJkxECvg6clImtOY@krava> (raw)
In-Reply-To: <5cafb729-1dcd-ad4a-507b-1155c16a785e@linux.intel.com>

On Thu, May 06, 2021 at 10:43:39PM +0800, Jin, Yao wrote:

SNIP

> > > '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
> > 
> 
> The challenge for us is if we need to compatible with the old perf.data
> which was generated by old perf tool.
> 
> For the old perf.data, the layout in header is:
> 
> nr of caps
> caps string 1
> caps string 2
> ...
> caps string N
> 
> It doesn't carry with any other fields such as size of caps data.
> 
> To be compatible with old perf.data, so I have to extend the layout to:
> 
> nr of caps for pmu 1
> caps string 1
> caps string 2
> ...
> caps string N
> name of pmu 1
> nr of rest pmus
> 
> nr of caps for pmu2
> caps string 1
> caps string 2
> ...
> caps string N
> name of pmu 2
> nr of rest pmus
> 
> When the new perf tool detects the string such as "cpu_", it can know that
> it's the pmu name field in new perf.data, otherwise it's the old perf.data.

what if the cap string starts with 'cpu_' ?

I think it might be better to create new feature that
stores caps for multiple pmus in generic way

> 
> If we add new field such as "size" to the layout, I'm afraid the new perf
> tool can not process the old perf.data correctly.
> 
> If we don't need to support old perf.data, that makes things easy.

we need to

jirka


  reply	other threads:[~2021-05-10 13:15 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
2021-05-06 14:43         ` Jin, Yao
2021-05-10 13:11           ` Jiri Olsa [this message]
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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