linux-kernel - RE: [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring buffer while reading trace file

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Date:   Fri, 27 Mar 2020 14:56:08 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Steven Rostedt' <rostedt@...dmis.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Alexei Starovoitov" <alexei.starovoitov@...il.com>,
        Peter Wu <peter@...ensteyn.nl>,
        Jonathan Corbet <corbet@....net>,
        Tom Zanussi <zanussi@...nel.org>,
        "Shuah Khan" <shuahkhan@...il.com>, bpf <bpf@...r.kernel.org>
Subject: RE: [PATCH 00/12 v2] ring-buffer/tracing: Remove disabling of ring
 buffer while reading trace file

From: Steven Rostedt
> Sent: 27 March 2020 14:31
..
> > Along with the one that lets you read the raw trace and get EOF.
> 
> Can you explain this more? I think we talked about this before, but I don't
> remember the details.

I was trying to use schedviz (on github from google).
It reads out the raw trace (for some scheduler events)
and then postprocesses it to generate to nice pictures.
However the shell script it uses for the captures has to run the
copies in the background, sleep a random time, and then kill all
the copies having hoped it has waited long enough - truly horrid.

There is also some confusion (IIRC between a header and your library
code) about the 'time-delta' on 'pad' entries.

	David

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