linux-kernel - Re: [PATCH v3 3/7] perf tools: Remove the logical that skip buildid cache if symfs is given

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Date:	Thu, 12 May 2016 17:33:55 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
	He Kuang <hekuang@...wei.com>, peterz@...radead.org,
	mingo@...hat.com, alexander.shishkin@...ux.intel.com,
	jolsa@...hat.com, wangnan0@...wei.com, jpoimboe@...hat.com,
	ak@...ux.intel.com, eranian@...gle.com, namhyung@...nel.org,
	adrian.hunter@...el.com, sukadev@...ux.vnet.ibm.com,
	masami.hiramatsu.pt@...achi.com, tumanova@...ux.vnet.ibm.com,
	kan.liang@...el.com, penberg@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/7] perf tools: Remove the logical that skip buildid
 cache if symfs is given

Em Thu, May 12, 2016 at 02:23:37PM -0600, David Ahern escreveu:
> On 5/12/16 7:09 AM, Arnaldo Carvalho de Melo wrote:
> > Em Thu, May 12, 2016 at 08:43:12AM +0000, He Kuang escreveu:
> > > Symfs dir and buildid dir are two places that perf looks into for
> > > symbols, currently, if symfs dir is given, buildid-cache is skipped.

> > > In the cross-platform perf record/script scenario, we need vdsos in
> > > buildid-cache dir and other libs in symfs dir at the same time. And
> > > consider that the binaries indexed by buildid do not cause ambiguity,
> > > this patch simply removes that logical.

> > Makes perfect sense, David, do you have any concern? Can I have your
> > Acked-by?

> seems odd to me you want to look in the buildid-cache when a symfs is given.
> The point of symfs was "go look for everything under here."

> I believe dso__load is going to hit DSO_BINARY_TYPE__BUILD_ID_CACHE before
> any of the others and there are probably cases where a stale cache entry
> would be hit before a build tree entry (e.g., symfs).

Stale cache entry? How'd that be? Its content based, i.e. if there is an
entry for a given build id _anywhere_ why wouldn't we want to use it?
 
> What about putting the build id cache under the symfs? so instead of
> dropping the symfs check and it to the path for the build id cache.

Well, the use case of look at both still looks sane to me, but maybe the
way you suggest works for He, He?

- Arnaldo