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Date: Fri, 26 Sep 2003 16:19:45 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: Maciej Zenczykowski <maze@cela.pl>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Syscall security
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On Fri, 26 Sep 2003, Maciej Zenczykowski wrote:

> Unfortunately sometimes the data transfer through stdio can be counted
> in hundreds of MB (or even in extreme cases a couple of GB), plus it is
> important to not slow down the execution of the code (we're timing and
> comparing execution speed of different approaches).  Would doing this
> via ptrace increase the runtime of the parent pid or of the child pid or
> both?  ie. would this make any syscall costly timewise (stdio is either
> from a ram disk or piped to/from a generating/checking process) or would
> this be unnoticeable?

you can measure this effect by doing "strace -o /dev/null <program>" of
such a program. (strace will have higher overhead than a simple syscall
filtering ptrace app, but it should show you the kind of effects ptrace
causes.)

	Ingo
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