linux-kernel - Re: multi-second application stall in open()

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Message-ID: <20120626125953.GA22557@redhat.com>
Date:	Tue, 26 Jun 2012 08:59:53 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Josh Hunt <joshhunt00@...il.com>
Cc:	Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	linux-kernel@...r.kernel.org
Subject: Re: multi-second application stall in open()

On Mon, Jun 25, 2012 at 11:01:48PM -0500, Josh Hunt wrote:

[..]
> So this really seems like a problem with kblockd not kicking in. I've
> instrumented every path in select_queue and it's not getting hit after
> schedule dispatch. Everything seems to stall at that point until a new
> request comes in.

Ok, that's cool. So now we need to find out why queued work is not being
scheduled.

I think there are some workqueue related trace points. If you enable those
along with blktraces, that should give tejun some data to look at.

Thanks
Vivek
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