linux-kernel - Re: [PATCH] perf tool: Fix ppid for synthesized fork events

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Date:	Wed, 25 Mar 2015 09:03:38 -0600
From:	David Ahern <dsahern@...il.com>
To:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
	Joe Mario <jmario@...hat.com>
CC:	Don Zickus <dzickus@...hat.com>, linux-kernel@...r.kernel.org,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] perf tool: Fix ppid for synthesized fork events

On 3/25/15 7:24 AM, Arnaldo Carvalho de Melo wrote:
> So it starts when there are tons of threads in the system, for which
> synthezing from /proc will have to take place, without looking again at
> that patch, I can't think about what would be a problem :-\

3 extra lines are read from /proc/pid/status:

Name:	bash
State:	S (sleeping)
Tgid:	6046

< current patch breaks here>

Ngid:	0
Pid:	6046
PPid:	6045

< my patch reads these 3 lines, repeats the memcmp and does an atoi on 
the PPid: value >

Let me remove that loop by reading in 4k at a time and making a single 
pass. That should bring down the overhead, but filling in the ppid will 
add some.

David

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