linux-kernel - Re: No, really, stop trying to delete slab until you've finished making slub perform as well

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Message-ID: <20080804152146.GG18868@shareable.org>
Date:	Mon, 4 Aug 2008 16:21:46 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Matthew Wilcox <matthew@....cx>,
	Pekka Enberg <penberg@...helsinki.fi>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Mel Gorman <mel@...net.ie>,
	andi@...stfloor.org, Rik van Riel <riel@...hat.com>
Subject: Re: No, really, stop trying to delete slab until you've finished making slub perform as well

Jamie Lokier wrote:
> Vaguely on this topic, has anyone studied the effects of SLAB/SLUB
> etc. on MMUless systems?

The reason is that MMU-less systems are extremely sensitive to
fragmentation.  Every program started on those systems must allocate a
large contiguous block for the code and data, and every malloc >1 page
is the same.  If memory is too fragmented, starting new programs fails.

The high-order page-allocator defragmentation lately should help with
that.

The different behaviours of SLAB/SLUB might result in different levels
of fragmentation, so I wonder if anyone has compared them on MMU-less
systems or fragmentation-sensitive workloads on general systems.

Thanks,
-- Jamie
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