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Subject: Re: IO scheduler based IO controller V10
From: Mike Galbraith <efault@gmx.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <jens.axboe@oracle.com>, Ingo Molnar <mingo@elte.hu>,
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Date: Fri, 02 Oct 2009 16:45:42 +0200
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On Fri, 2009-10-02 at 07:24 -0700, Linus Torvalds wrote:
> 
> On Fri, 2 Oct 2009, Jens Axboe wrote:
> > 
> > It's really not that simple, if we go and do easy latency bits, then
> > throughput drops 30% or more.
> 
> Well, if we're talking 500-950% improvement vs 30% deprovement, I think 
> it's pretty clear, though. Even the server people do care about latencies. 
> 
> Often they care quite a bit, in fact.
> 
> And Mike's patch didn't look big or complicated.

But it is a hack.  (thought about and measured, but hack nonetheless)

I haven't tested it on much other than reader vs streaming writer.  It
may well destroy the rest of the IO universe. I don't have the hw to
even test any hairy chested IO.

	-Mike