From: NeilBrown <neilb@suse.de>
To: Ethan Wilson <ethan.wilson@shiftmail.org>
Cc: "linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>
Subject: Re: RAID456 direct I/O write performance
Date: Tue, 9 Sep 2014 13:24:31 +1000 [thread overview]
Message-ID: <20140909132431.24456db1@notabene.brown> (raw)
In-Reply-To: <5408D5CC.101@shiftmail.org>
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On Thu, 04 Sep 2014 23:12:44 +0200 Ethan Wilson <ethan.wilson@shiftmail.org>
wrote:
> OTOH I would like to ask kernel experts one thing if I may: does anybody
> know a way to get a stack trace for a process which is currently running
> in kernel mode and is running NOW on a CPU and it is not stopped waiting
> in a queue? I know about /proc/pid/stack but that one shows
> 0xffffffffffffffff for such a case. Being able to do that would help to
> answer the above question too...
The contents of the stack would change while it was being inspected, so it
would be impossible to get a meaningful trace.
Maybe you could disable all but one CPU. Then whenever you try to look at
the stack of another process it must have scheduled and so will have a
stable visible stack...
Or maybe you would use "perf record -g" to get some stack information, I'm
not sure.
NeilBrown
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prev parent reply other threads:[~2014-09-09 3:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-04 16:23 RAID456 direct I/O write performance Markus Stockhausen
2014-09-04 16:30 ` AW: " Markus Stockhausen
2014-09-04 21:12 ` Ethan Wilson
2014-09-05 18:06 ` AW: " Markus Stockhausen
2014-09-06 19:46 ` Markus Stockhausen
2014-09-09 3:24 ` NeilBrown [this message]
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