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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Christoph Lameter <clameter@sgi.com>
Subject: Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK
Date: Fri, 28 Sep 2007 07:42:37 +1000
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Cc: Christoph Hellwig <hch@lst.de>, Mel Gorman <mel@skynet.ie>,
       linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       David Chinner <dgc@sgi.com>, Jens Axboe <jens.axboe@oracle.com>
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On Wednesday 19 September 2007 13:36, Christoph Lameter wrote:
> SLAB_VFALLBACK can be specified for selected slab caches. If fallback is
> available then the conservative settings for higher order allocations are
> overridden. We then request an order that can accomodate at mininum
> 100 objects. The size of an individual slab allocation is allowed to reach
> up to 256k (order 6 on i386, order 4 on IA64).

How come SLUB wants such a big amount of objects? I thought the
unqueued nature of it made it better than slab because it minimised
the amount of cache hot memory lying around in slabs...

vmalloc is incredibly slow and unscalable at the moment. I'm still working
on making it more scalable and faster -- hopefully to a point where it would
actually be usable for this... but you still get moved off large TLBs, and
also have to inevitably do tlb flushing.

Or do you have SLUB at a point where performance is comparable to SLAB,
and this is just a possible idea for more performance?
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