linux-kernel - Re: [PATCH 3/4] writeback: replace custom worker pool implementation with unbound workqueue

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Message-ID: <20130321015721.GL17758@dastard>
Date:	Thu, 21 Mar 2013 12:57:21 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jan Kara <jack@...e.cz>, axboe@...nel.dk, laijs@...fujitsu.com,
	fengguang.wu@...el.com, linux-kernel@...r.kernel.org,
	jmoyer@...hat.com
Subject: Re: [PATCH 3/4] writeback: replace custom worker pool implementation
 with unbound workqueue

On Tue, Mar 19, 2013 at 10:28:24AM -0700, Tejun Heo wrote:
> Hello, Jan.
> 
> On Tue, Mar 19, 2013 at 8:46 AM, Jan Kara <jack@...e.cz> wrote:
> >   Well, but what you often get is just output of sysrq-w, or sysrq-t, or
> > splat from scheduler about stuck task. You often don't have the comfort of
> > tracing... Can't we somehow change 'comm' of the task when it starts
> > processing work of some bdi?
> 
> You sure can but I'd prefer not to do that. If you wanna do it
> properly, you have to grab task lock every time a work item starts
> execution. I'm not sure how beneficial having the block device
> identifier would be. Backtrace would be there the same. Is identifying
> the block device that important?

When you have a system that has 50+ active filesystems (pretty
common in the distributed storage environments were every disk has
it's own filesystem), knowing which filesystem(s) are getting stuck
in writeback from the sysrq-w or hangcheck output is pretty damn
important....

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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