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RE: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling forfast paths"
- To: "Luck, Tony" <tony.luck@xxxxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>
- From: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
- Date: Wed, 23 Nov 2005 09:49:05 -0800
- Cc: Xen Mailing List <xen-devel@xxxxxxxxxxxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, linux-ia64@xxxxxxxxxxxxxxx, Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>, David Mosberger-Tang <David.Mosberger@xxxxxxx>
- Delivery-date: Wed, 23 Nov 2005 17:50:42 +0000
- List-id: Xen developer discussion <xen-devel.lists.xensource.com>
- Thread-index: AcXwDmS/56OkMzn6Rb2y1vOGnL1rKQAMQsXgAAUEb9A=
- Thread-topic: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling forfast paths"
> Subject: RE: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix
> ar.unat handling forfast paths"
> >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?
Since this thread is cross-posted to two lists neither one of which
is xen-ia64-devel, a short explanation might be in order:
Since there a fair overlap of functionality, Xen/ia64 heavily
leverages Linux and Linux/ia64 code. About 120 .c/.h files are
100% reused from linux-2.6.13 and another 36 files are
reused but require small patches (total of ~120 chunks, mostly
1-2 line diffs). The leveraged files are periodically updated
to use the latest version of linux (started with 2.6.7, then 2.6.9,
now 2.6.13); this allows Xen/ia64 to easily pick up new functionality
and bug fixes from Linux/ia64 without reinventing the wheel.
HOWEVER, one disadvantage is that some bugs in Linux get inherited
by Xen/ia64. As Tony previously noted, Linux/ia64 makes some
assumptions about SMP_CACHE_BYTES which are not adhered to throughout
Linux. Xen apparently does not adhere to those assumptions either.
Xen/ia64 will need to add another patch to the (previously unchanged)
file linux/include/asm-ia64/cache.h. Presumably this should
be fixed in Linux/ia64 as well and the file will be resynced
in the future.
Hope that helps!
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