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Date: Thu, 26 Apr 2007 17:17:54 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Christoph Lameter <clameter@sgi.com>
CC: David Chinner <dgc@sgi.com>, "Eric W. Biederman" <ebiederm@xmission.com>,
       linux-kernel@vger.kernel.org, Mel Gorman <mel@skynet.ie>,
       William Lee Irwin III <wli@holomorphy.com>,
       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> <Pine.LNX.4.64.0704252337390.30340@schroedinger.engr.sgi.com> <46304C74.9040304@yahoo.com.au> <20070426070454.GF32602149@melbourne.sgi.com> <46304FAF.7020700@yahoo.com.au> <Pine.LNX.4.64.0704260011140.30731@schroedinger.engr.sgi.com>
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Christoph Lameter wrote:
> On Thu, 26 Apr 2007, Nick Piggin wrote:
> 
> 
>>>Nick, what's the buffer layer? Are you talking about operations
>>>based on bufferheads?
>>
>>Yeah. Our pgoff_t->sector_t translation.
> 
> 
> Sadly the buffers in the buffer layer still assume contiguous memory. You 
> would have to add a series of pointers there and then add a layer to 
> handle this.

That's the least of the problems with rewriting the buffer layer.

But I maintain that the end result is better than the fragmentation
based approach. A lot of people don't actually want a bigger page
cache size, because they want efficient internal fragmentation as
well, so your radix-tree based approach isn't really comparable.

-- 
SUSE Labs, Novell Inc.