linux-kernel - Re: [patch 1/3] raid5: offload stripe handle to workqueue

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Message-ID: <20130730135751.GD12016@htj.dyndns.org>
Date:	Tue, 30 Jul 2013 09:57:51 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Shaohua Li <shli@...nel.org>
Cc:	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	neilb@...e.de, djbw@...com
Subject: Re: [patch 1/3] raid5: offload stripe handle to workqueue

Hello,

On Tue, Jul 30, 2013 at 09:07:08PM +0800, Shaohua Li wrote:
> Ok, I should explain here. I can't add a work_struct for each stripe, because
> this will stress workqueue very hard. My system handles > 1M/s stripes, which
> makes workqueue pool lock contended very hard.

It doesn't have to be embedding work_struct in each stripe and
schduling them altogether.  It's more about scheduling "work units"
rather than "workers" - ie. letting each scheduled work item handle
single work unit rather than making it dispatch multiple work items.
It may make controlling concurrency a bit more interesting but you can
always do it with workqueue_set_max_active(), which is the intended
usage anyway.

Thanks.

-- 
tejun
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