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Re: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling forfa

To: "Luck, Tony" <tony.luck@xxxxxxxxx>
Subject: Re: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling forfast paths"
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 23 Nov 2005 15:37:07 +0000
Cc: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, Xen Mailing List <xen-devel@xxxxxxxxxxxxxxxxxxx>, linux-ia64@xxxxxxxxxxxxxxx, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>, djm@xxxxxxxxxxxxxxx, David Mosberger-Tang <David.Mosberger@xxxxxxx>
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On 23 Nov 2005, at 15:07, Luck, Tony wrote:

It's not hard to support arbitrary alignment, at the cost of burning
some space. We should probably do that.

The "we" in that last sentence is the Xen team ... referring
to making fixes to xmalloc?

Correct. But I've thought more on it and I guess that actually the number of cases where we have structures with alignment requirements stricter than SMP_CACHE_BYTES will be very small. In fact I can't think of any in Xen right now. :-)

So it makes most sense for ia64 Xen to define SMP_CACHE_BYTES to a sensible largeish number irrespective of CONFIG_SMP (after all, how many uniproc ia64 systems are there), and solve the general alignment problem in xmalloc only if we really need to.

 -- Keir


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