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

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Message-ID: <Pine.LNX.4.64.0704292225540.1978@schroedinger.engr.sgi.com>
Date:	Sun, 29 Apr 2007 22:30:46 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	David Chinner <dgc@....com>, linux-kernel@...r.kernel.org,
	Mel Gorman <mel@...net.ie>,
	William Lee Irwin III <wli@...omorphy.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Badari Pulavarty <pbadari@...il.com>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [00/17] Large Blocksize Support V3

On Fri, 27 Apr 2007, Andrew Morton wrote:

> By misunderstanding any suggestions, misrepresenting them, making incorrect
> statements about them, by not suggesting any alternatives yourself, all of
> it buttressed by a stolid refusal to recognise that this patch has any
> costs.

That was even mentioned in the initial post.... Definitely it would 
require significant changes but getting there is fairly straightforward 
with the use of compound pages.
 
> This effectively leaves it up to others to find time to think about and to
> implement possible alternative solutions to the problems which you're
> observing.

They are working on other problems like radix tree scalability it seems. 

> The altenative which is on the table (and there may be others) is
> populating pagecache with physically contiguous pages.  This will fix the
> HBA problem and is much less costly in terms of maintenance and will
> improve all workloads on all machines and doesn't have the additional
> runtime costs of pagecache wastage and more memset() overhead with small
> files and it doesn't require administrator intervention.
> 
> OTOH (yes!  there are tradeoffs!) it will consume an unknown amount more
> CPU and it doesn't address the large-fs-blocksize requirement, but I don't
> know how important the latter is and given the unrelenting advocacy storm
> coming from the SGI direction I don't know how to find that out, frankly.

This is certainly a nice approach if it works and may address one 
issue that motivated this patchset but it does not address all.

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