From: Ingo Molnar <mingo@elte.hu>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: linux-kernel@vger.kernel.org, systemtap@sources.redhat.com,
"Frank Ch. Eigler" <fche@redhat.com>
Subject: Re: System call instrumentation
Date: Mon, 5 May 2008 14:28:35 +0200 [thread overview]
Message-ID: <20080505122835.GA1523@elte.hu> (raw)
In-Reply-To: <20080505113057.GA28070@Krystal>
* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> Ideally, I'd like to have this kind of high-level information :
>
> event name : kernel syscall
> syscall name : open
> arg1 (%s) : "somefile" <-----
> arg2 (%d) : flags
> arg3 (%d) : mode
>
> However, "somefile" has to be read from userspace. With the protection
> involved, it would cause a performance impact to read it a second time
> rather than tracing the string once it's been copied to kernel-space.
performance is a secondary issue here, and copies are fast anyway _if_
someone wants to trace a syscall. (because the first copy brings the
cacheline into the cache, subsequent copies are almost for free compared
to the first copy)
Ingo
next prev parent reply other threads:[~2008-05-05 12:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-04 13:48 System call instrumentation Mathieu Desnoyers
2008-05-05 6:55 ` Ingo Molnar
2008-05-05 10:59 ` Mathieu Desnoyers
2008-05-05 11:10 ` Ingo Molnar
2008-05-05 11:30 ` Mathieu Desnoyers
2008-05-05 12:28 ` Ingo Molnar [this message]
2008-05-06 20:52 ` Masami Hiramatsu
2008-05-20 3:44 ` Mathieu Desnoyers
2008-05-20 14:18 ` Arjan van de Ven
2008-05-22 12:47 ` Mathieu Desnoyers
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