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Date: Fri, 27 Apr 2007 19:46:28 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: William Lee Irwin III <wli@holomorphy.com>
CC: David Chinner <dgc@sgi.com>, "Eric W. Biederman" <ebiederm@xmission.com>,
       clameter@sgi.com, linux-kernel@vger.kernel.org,
       Mel Gorman <mel@skynet.ie>, Jens Axboe <jens.axboe@oracle.com>,
       Badari Pulavarty <pbadari@gmail.com>,
       Maxim Levitsky <maximlevitsky@gmail.com>
Subject: Re: [00/17] Large Blocksize Support V3
References: <20070424222105.883597089@sgi.com> <m1hcr3oi0m.fsf@ebiederm.dsl.xmission.com> <46303A98.9000605@yahoo.com.au> <20070426063830.GE32602149@melbourne.sgi.com> <m1k5vzmoo7.fsf@ebiederm.dsl.xmission.com> <20070426135033.GU65285596@melbourne.sgi.com> <4630C776.9000804@yahoo.com.au> <20070426155840.GU31925@holomorphy.com>
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William Lee Irwin III wrote:
> On Fri, Apr 27, 2007 at 01:38:30AM +1000, Nick Piggin wrote:
> 
>>Or good grounds to increase the sg limit and push for io controller
>>manufacturers to do the same. If we have a hack in the kernel that
>>mostly works, they won't.
> 
> 
> On Fri, Apr 27, 2007 at 01:38:30AM +1000, Nick Piggin wrote:
> 
>>Page colouring was always rejected, and lots of people who knew
>>better got upset because it was the only way the hardware would go
>>fast...
> 
> 
> Yes, stunning wisdom there. Reject the speedups.

Yeah, that's how lots of people felt. But there is a good argument
to do just that.


> On Fri, Apr 27, 2007 at 01:38:30AM +1000, Nick Piggin wrote:
> 
>>You could put it that way. Or that it is wrong because of the
>>fragmenatation problem. Realise that it is somewhat fundamental
>>considering that it is basically an unsolvable problem with our
>>current kernel assumptions of unconstrained kernel allocations and
>>a 1:1 kernel mapping.
> 
> 
> Depends on what you consider a solution. A broadly used criterion is
> that improves performance significantly in important usage cases.

My criterion is that you are not suddenly unable to access your
filesystem because you cannot allocate a higher order page.

-- 
SUSE Labs, Novell Inc.