RE: [Xen-devel] [PATCH] x86: add SSE-based copy_page()

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Thanks Dexuan!  I don't want to flush the TLB (which
wbinvd does) so it looks like the way to flush cache
on a page in Xen is:

#include <xen/flushtlb.h>
flush_area_local(va,FLUSH_CACHE|FLUSH_ORDER(0))


> -----Original Message-----
> From: Cui, Dexuan [mailto:dexuan.cui@xxxxxxxxx]
> Sent: Thursday, November 13, 2008 8:08 PM
> To: Dan Magenheimer; Jan Beulich
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] [PATCH] x86: add SSE-based copy_page()
>
>
> Hi Dan,
> clflush(flush a cache line; you may need a loop to flush a
> page.) or wbinvd(flush all the caches) should be what you
> need to flush caches on x86.
>
> Thanks,
> -- Dexuan
>
>
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
> Dan Magenheimer
> Sent: 2008年11月14日 7:42
> To: Jan Beulich
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] [PATCH] x86: add SSE-based copy_page()
>
> > This very much depends on whether the page(s) are in any caches - in
> > the general case (e.g. when dealing with large sets of data, or data
> > just read from disk), you'd expect both pages (source and
> destination)
> > not to be in any cache. This is where using the streaming
> instructions
> > helps.
> >
> > However, when dealing with a small set of pages (or even
> just a single
> > source/destination pair), you'd easily run entirely on L1 or
> > L2 data, which
> > certainly performs better using the non-streaming instructions.
>
> Is there a way to force-flush-cache on a page full of data?  (I knew
> how to do this once on ia64...)  I can easily measure warm-start but
> am not sure how to measure cold-start without some kind of flush.
>
> Thanks,
> Dan
>
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