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

To: "Tian, Kevin" <kevin.tian@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 08:54:46 +0000
Cc: "Luck, Tony" <tony.luck@xxxxxxxxx>, linux-ia64@xxxxxxxxxxxxxxx, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>, djm@xxxxxxxxxxxxxxx, Xen Mailing List <xen-devel@xxxxxxxxxxxxxxxxxxx>, David Mosberger-Tang <David.Mosberger@xxxxxxx>
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On 23 Nov 2005, at 02:58, Tian, Kevin wrote:

Now I think even '16' can't cover all cases. It's possible for a user defined structure with .align directive to force by '32' or larger, and then allocator happens to have similar check upon SMP_CACHE_BYTES like case in this thread. Because both structure definition and allocator may have no idea about IA64 trick of saving space for UP. Max alignment of any C style only solves the natural alignment case, but not above forced one. We can just give its real assumption to SMP_CACHE_BYTES - cache line size. ;-)

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

 -- Keir


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