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Message-ID: <20100903060927.GA19074@elte.hu>
Date: Fri, 3 Sep 2010 08:09:27 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Eric B Munson <emunson@...bm.net>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
akpm@...ux-foundation.org, mingo@...hat.com,
hugh.dickins@...cali.co.uk, riel@...hat.com, peterz@...radead.org,
anton@...ba.org, hch@...radead.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [PATCH 1/2] Add trace points to mmap, munmap, and brk
* Eric B Munson <emunson@...bm.net> wrote:
> Sorry for the long delay, the enter/exit routines are not compatible
> with the information that these new trace points provides. When
> tracing mmap, for instance, the addr and len arguments can be altered
> by the function. If you use the enter/exit trace points you would not
> see this as the arguments are sampled at function entrance and not
> given again on exit. Also, the new trace points are only hit on
> function success, the exit trace point happens any time you leave the
> system call.
Would it be feasible to use enter/exit information as the main source of
events - and only add new tracepoints for the _missing_ information?
(such as when mmap arguments change)
Then user-space can combine the two. The new tracepoints would also
carry useful information in themselves: they would show the cases where
user-space did not get what it wished. (or so)
Thanks,
Ingo
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