RE: [Xen-devel] __ia64__ ifdef in xmalloc.c: "Fix ar.unat handling forfast paths"

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

> 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?
> 
> -Tony

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!

Dan

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