linux-kernel - Re: [PATCH 0/8][RFC] IO latency/throughput fixes

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Message-ID: <20090406170116.GH5178@kernel.dk>
Date:	Mon, 6 Apr 2009 19:01:16 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	tytso@....edu
Subject: Re: [PATCH 0/8][RFC] IO latency/throughput fixes

On Mon, Apr 06 2009, Linus Torvalds wrote:
> 
> 
> On Mon, 6 Apr 2009, Jens Axboe wrote:
> >
> > > Jens - I can just apply this queue (I want to test it out anyway), or if 
> > > you prefer I can pull from you. Just tell me.
> > 
> > Whatever you want, if you want to pull instead of manually applying,
> > it's:
> > 
> > git://git.kernel.dk/linux-2.6-block.git blk-latency
> 
> Ok, I applied them for testing anyway, so I think I'll just keep the 
> series I have in my tree. I'm keeping my nasty "dd+sync" going in the 

No problem, the end result should be identical :-)

> background, just to verify that things really feel better, but I'm already 
> convinced this is a winner. Especially with the request size limiter, I 
> can really read email _almost_ as if nothing else was going on on the 
> machine. 
> 
> With that request size limiting, my fsync pauses tend to be in the 250ms 
> range, with a one 0.75s outlier in the last few minutes. I can definitely 
> feel that quarter-second thing, and the .75s pause was a real stutter, but 
> boy what a difference. I don't get the uncontrollable urge to kill that 
> nasty background writer any more.

If we can make the dd writer almost unnoticable, then I think we've come
a long way already. That really is a nasty workload.

-- 
Jens Axboe

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