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

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Date:	Tue, 11 Sep 2007 16:06:09 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Christoph Lameter <clameter@....com>
Cc:	Mel Gorman <mel@....ul.ie>, andrea@...e.de,
	torvalds@...ux-foundation.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
	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>,
	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 Wednesday 12 September 2007 07:41, Christoph Lameter wrote:
> On Tue, 11 Sep 2007, Nick Piggin wrote:
> > I think I would have as good a shot as any to write a fragmentation
> > exploit, yes. I think I've given you enough info to do the same, so I'd
> > like to hear a reason why it is not a problem.
>
> No you have not explained why the theoretical issues continue to exist
> given even just considering Lumpy Reclaim in .23 nor what effect the
> antifrag patchset would have.

So how does lumpy reclaim, your slab patches, or anti-frag have
much effect on the worst case situation? Or help much against a
targetted fragmentation attack?


> And you have used a 2M pagesize which is 
> irrelevant to this patchset that deals with blocksizes up to 64k. In my
> experience the use of blocksize < PAGE_COSTLY_ORDER (32k) is reasonably
> safe.

I used EXACTLY the page sizes that you brought up in your patch
description (ie. 64K and 2MB).
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