From: Maxim Uvarov <muvarov@ru•mvista.com>
To: Linas Vepstas <linas@austin•ibm.com>
Cc: linuxppc-dev@ozlabs•org,
Andrew Morton <akpm@linux-foundation•org>,
pavel@ucw•cz, wli@holomorphy•com, dada1@cosmosbay•com
Subject: Re: Using kprobes [was Re: [PATCH] Performance Stats: Kernel patch
Date: Mon, 21 May 2007 15:28:27 +0000 [thread overview]
Message-ID: <4651BA9B.6040108@ru.mvista.com> (raw)
In-Reply-To: <20070511172304.GI4452@austin.ibm.com>
Linas Vepstas wrote:
>On Thu, May 10, 2007 at 11:12:42AM -0700, Andrew Morton wrote:
>
>
>>I don't think the syscall-counting feature has a future, sorry. Perhaps
>>you could do something like hooking it up on-demand by insertion of a kprobe,
>>dunno.
>>
>>
>
>This is an interesting point. I've started fiddling with (a wrapper
>around) kprobes that allows me to pick any subroutine symbol in System.map,
>and then get an event whenever that subroutine gets called. Its pretty
>slick, and allows me to gather data on certain unusual events in the
>kernel. (I'm not using this for performance monitoring, I'm trying to
>do RAS).
>
>It makes a lot of sense to me to have a generic kprobe extension, where
>you could give it a list of subroutine names, and it'll collect stats
>on the number of times that the routine was called. Some user-space thingy
>could poll for those stats, or you could put them in /sys or wherever.
>
>Its more complicted than just instriumenting syscalls, but a lot more
>useful, I would think ...
>
>--linas
>
>
>
Thanks Linas, but do you think that kprobes is safe for syscall counting?
I think that the overhead will be much bigger in that case. In my case it is
1 line asm instruction and it is defended with #ifdefs.
Kprobes is very good thing. But is not clear for me how to count
per-thread statistics.
In my case I increased struct thread_info. In case with kprobes it is
easy to count all
do_fork execution, for example, but not for each thread. And in any
case, place for keeping this
counters is needed.
Maxim.
next prev parent reply other threads:[~2007-05-21 11:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-08 16:26 [PATCH] Performance Stats: Kernel patch Maxim Uvarov
2007-05-08 19:32 ` Andrew Morton
2007-05-10 11:11 ` Maxim Uvarov
2007-05-10 18:12 ` Andrew Morton
2007-05-11 16:51 ` Maxim Uvarov
2007-05-11 17:23 ` Using kprobes [was " Linas Vepstas
2007-05-12 9:15 ` Christoph Hellwig
2007-05-21 15:28 ` Maxim Uvarov [this message]
2007-05-08 23:32 ` Linas Vepstas
2007-05-10 10:22 ` Maxim Uvarov
2007-05-10 16:47 ` Linas Vepstas
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