linux-kernel - Re: [00/17] Large Blocksize Support V3

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Date:	Thu, 26 Apr 2007 16:57:20 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Christoph Lameter <clameter@....com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@...net.ie>,
	William Lee Irwin III <wli@...omorphy.com>,
	David Chinner <dgc@....com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Badari Pulavarty <pbadari@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>
Subject: Re: [00/17] Large Blocksize Support V3

Christoph Lameter wrote:
> On Thu, 26 Apr 2007, Nick Piggin wrote:
> 
> 
>>Yeah. IMO anti-fragmentation and defragmentation is the hack, and we
>>should stay away from higher order allocations whenever possible.
> 
> 
> Right and we need to create series of other approaches that we then label 
> "non-hack" to replace it. 

I don't understand? We're talking about several utterly different designs
to approach these problems. You don't agree that one might be better than
another?


>>Hardware is built to handle many small pages efficintly, and I don't
>>understand how it could be an SGI-only issue. Sure, you may have an
>>order of magnitude or more memory than anyone else, but even my lowly
>>desktop _already_ has orders of magnitude more pages than it has TLB
>>entries or cache -- if a workload is cache-nice for me, it probably
>>will be on a 1TB machine as well, and if it is bad for the 1TB machine,
>>it is also bad on mine.
> 
> 
> There have been numbers of people that have argued the same point. Just 
> because we have developed a way of thinking to defend our traditional 4k 
> values does not make them right.
> 
> 
>>If this is instead an issue of io path or reclaim efficiency, then it
>>would be really nice to see numbers... but I don't think making these
>>fundamental paths more complex and slower is a nice way to fix it
>>(larger PAGE_SIZE would be, though).
> 
> 
> The code paths can stay the same. You can switch CONFIG_LARGE pages off
> if you do not want it and it is as it was.

That isn't a good reason to merge something. If you don't have numbers then
that just seems incredible.


> If you would have a look the patches: The code is significantly cleanup 
> and easier to read.

Cleanups are fine.

-- 
SUSE Labs, Novell Inc.
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