linux-kernel - Re: [00/41] Large Blocksize Support V7 (adds memmap support)

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Message-ID: <Pine.LNX.4.64.0709131934310.12159@schroedinger.engr.sgi.com>
Date:	Thu, 13 Sep 2007 19:38:16 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Mel Gorman <mel@...net.ie>
cc:	Nick Piggin <nickpiggin@...oo.com.au>, andrea@...e.de,
	torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
	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>,
	Fengguang Wu <fengguang.wu@...il.com>,
	swin wang <wangswin@...il.com>, totty.lu@...il.com,
	hugh@...itas.com, joern@...ybastard.org
Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support)

On Thu, 13 Sep 2007, Mel Gorman wrote:

> Surely, we'll be able to detect the situation where the memory is really
> contiguous as a fast path and have a slower path where fragmentation was
> a problem.

Yes I have a draft here now of a virtual compound page solution that I am 
testing with SLUB. Page allocator first tries to allocate a contiguous 
page. If that is not possible then we string together a contiguous page 
through order 0 allocs and vmalloc.

> The only implementation question about these patches that hasn't been addressed
> is the mmap() support. What's wrong with it in it's current form. Can it be
> fixed or if it's fundamentally screwed etc. That has fallen by the
> wayside.

Yes I have not heard about those. Got some more ideas how to clean it up 
even more in the meantime. No feedback usually means no objections..... 

> I am *very* wary of using reserve pools for anything other than
> emergency situations. If nothing else pools == wasted memory + a sizing
> problem. But hey, it is one option.

Well we need the page pools anyways for large page sizes > MAX_ORDER. But 

> Are we going to agree on some sort of plan or are we just going to
> handwave ourselves to death?

Ill try to do the virtual mapped compound pages. Hopefully that will 
allow fallback for compound pages in a generic way.
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