linux-kernel - Re: [RFT PATCH] blkio: alloc per cpu data from worker thread context( Re: kvm deadlock)

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Message-ID: <4EF0844A.4090600@kernel.dk>
Date:	Tue, 20 Dec 2011 13:49:14 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	Tejun Heo <tj@...nel.org>, Nate Custer <nate@...nel.net>,
	Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFT PATCH] blkio: alloc per cpu data from worker thread context(
 Re: kvm deadlock)

On 2011-12-19 19:27, Vivek Goyal wrote:
> I think reverting the previous series is not going to be simple either. It
> had 13 patches.
> 
> https://lkml.org/lkml/2011/5/19/560
> 
> By making stats per cpu, I was able to reduce contention on request
> queue lock. Now we shall have to bring the lock back. 

That's not going to happen, having that lock in there was a disaster for
small IO on fast devices. It's essentially the limiting factor on
benchmark runs on the RHEL kernels that have it included and enabled...


-- 
Jens Axboe

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