linux-kernel - Re: [RFC] Proposal for ptrace improvements

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Message-ID: <20110304161321.GB23553@redhat.com>
Date:	Fri, 4 Mar 2011 17:13:21 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Tejun Heo <tj@...nel.org>, Roland McGrath <roland@...hat.com>,
	jan.kratochvil@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org
Subject: Re: [RFC] Proposal for ptrace improvements

On 03/04, Denys Vlasenko wrote:
>
> # time sh -c './strace -e trace=exit_group ls -lR /usr/share >/dev/null'
> exit_group(0)                           = ?
> real	0m47.695s
> user	0m3.965s
> sys	0m29.047s
>
> strace with PTRACE_GETSIGINFO:
>
> # time sh -c './strace -e trace=exit_group ls -lR /usr/share >/dev/null'
> exit_group(0)                           = ?
> real	0m51.958s
> user	0m3.899s
> sys	0m31.584s

I am wondering how much ptrace_check_attach()->wait_task_inactive()
contributes... it can sleep.

And note that many ptrace requests do not really need this,
PTRACE_GETSIGINFO in particular.

Oleg.

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