linux-kernel - Re: [PATCH] perf dso: Fix dso comparison

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Message-ID: <20200324104843.GS1534489@krava>
Date:   Tue, 24 Mar 2020 11:48:43 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     acme@...nel.org, linux-kernel@...r.kernel.org, namhyung@...nel.org,
        mark.rutland@....com, naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [PATCH] perf dso: Fix dso comparison

On Tue, Mar 24, 2020 at 09:54:24AM +0530, Ravi Bangoria wrote:
> Perf gets dso details from two different sources. 1st, from builid
> headers in perf.data and 2nd from MMAP2 samples. Dso from buildid
> header does not have dso_id detail. And dso from MMAP2 samples does
> not have buildid information. If detail of the same dso is present
> at both the places, filename is common.
> 
> Previously, __dsos__findnew_link_by_longname_id() used to compare only
> long or short names, but Commit 0e3149f86b99 ("perf dso: Move dso_id
> from 'struct map' to 'struct dso'") also added a dso_id comparison.
> Because of that, now perf is creating two different dso objects of the
> same file, one from buildid header (with dso_id but without buildid)
> and second from MMAP2 sample (with buildid but without dso_id).
> 
> This is causing issues with archive, buildid-list etc subcommands. Fix
> this by comparing dso_id only when it's present. And incase dso is
> present in 'dsos' list without dso_id, inject dso_id detail as well.
> 
> Before:
> 
>   $ sudo ./perf buildid-list -H
>   0000000000000000000000000000000000000000 /usr/bin/ls
>   0000000000000000000000000000000000000000 /usr/lib64/ld-2.30.so
>   0000000000000000000000000000000000000000 /usr/lib64/libc-2.30.so
> 
>   $ ./perf archive
>   perf archive: no build-ids found
> 
> After:
> 
>   $ ./perf buildid-list -H
>   b6b1291d0cead046ed0fa5734037fa87a579adee /usr/bin/ls
>   641f0c90cfa15779352f12c0ec3c7a2b2b6f41e8 /usr/lib64/ld-2.30.so
>   675ace3ca07a0b863df01f461a7b0984c65c8b37 /usr/lib64/libc-2.30.so
> 
>   $ ./perf archive
>   Now please run:
> 
>   $ tar xvf perf.data.tar.bz2 -C ~/.debug
> 
>   wherever you need to run 'perf report' on.
> 
> Reported-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

looks good, do we need to add the dso_id check to sort__dso_cmp?

thanks,
jirka