linux-kernel - Re: perf tools: remove option --tail-synthesize ?

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Date:   Wed, 21 Nov 2018 10:11:56 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Wang Nan <wangnan0@...wei.com>
Cc:     Song Liu <songliubraving@...com>,
        lkml <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: perf tools: remove option --tail-synthesize ?

Em Wed, Nov 21, 2018 at 07:45:28AM +0000, Song Liu escreveu:
> Hi,
> 
> I found perf-record --tail-synthesize without --overwrite breaks symbols
> for perf-script, perf-report, etc. For example:
> 
> [root@]# ~/perf record -ag --tail-synthesize -- sleep 1
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 1.129 MB perf.data (3531 samples) ]
> [root@]# ~/perf script | head
> swapper     0 [000] 1250675.051971:          1 cycles:ppp:
>         ffffffff81009e15 [unknown] ([unknown])
>         ffffffff81196b19 [unknown] ([unknown])
>         ffffffff81196579 [unknown] ([unknown])
>         ffffffff81110ca7 [unknown] ([unknown])
>         ffffffff81a01f4a [unknown] ([unknown])
>         ffffffff81a017bf [unknown] ([unknown])
>         ffffffff8180e17a [unknown] ([unknown])
> 
> perf-record with --overwrite does NOT have this issue.
> 
> After digging into this, I found this issue is introduced by commit
> a73e24d240bc136619d382b1268f34d75c9d25ce.
> 
> Reverting this commit does fix this issue. However, on a second thought,
> I feel it is probably better just drop --tail-synthesize, as it doesn't
> make much sense without --overwrite. All we need is to do tail_synthesize
> when --overwrite is set.
> 
> Thoughts?

Wang, wdyt?

- Arnaldo