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Subject: Re: [PATCH v3 3/7] perf tools: Remove the logical that skip buildid
 cache if symfs is given
To: Hekuang <hekuang@huawei.com>,
        Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
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From: David Ahern <dsahern@gmail.com>
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Date: Fri, 13 May 2016 08:27:29 -0600
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On 5/13/16 1:19 AM, Hekuang wrote:
>> 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.
>>
>>
> I think your intention is to reference symbol files in one place
> instead of two. So there're two possible approaches, one is all
> in buildid-cache, but in practice, I found lots of binaries in
> symfs even not contains valid buildid, so this way is not work.
>
> The other one is all in symfs. It seems ok, but one problem I
> should point out, with my test environment as an example, the
> symfsdir is $(TARGET_ROOTFS),and by default buildid_dir is
> $(TARGET_ROOTFS)/$(HOME)/.debug/, host perf does not know
> $(HOME) folder in target and we should copy the debug folder
>  to $(TARGET_ROOTFS), which is readonly in the target. For me, it's
> easier to use 'buildid-cache -a vdso-xxxx' to add that into host
> buildid-cache than copy debug folder from $(HOME) to readonly
> $(TARGET_ROOTFS).
>
> Without the stale concern, I prefer the two places(buildid-dir in
> host and target symfs) way.

The intention of symfs is every single file opened by perf is relative 
to that directory. As I recall when I added that option in early 2011 I 
made sure that statement is true. I think it is best to maintain that 
design.