Re: [Xen-devel] Re: Even faster page copy for Xen?

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 09.08.10 at 19:57, Dulloor <dulloor@xxxxxxxxx> wrote:
> On Mon, Aug 9, 2010 at 10:47 AM, Dulloor <dulloor@xxxxxxxxx> wrote:
>> On Fri, Aug 6, 2010 at 12:57 AM, Jan Beulich <JBeulich@xxxxxxxxxx> wrote:
>>> I'm not sure how much of this applies to the much more specific
>>> case of copying pages... Additionally, I don't think trying to
>>> use XMM registers in Xen would be a good idea.
> 
>> Why would you say using xmm/sse in Xen is a bad idea ? We already have a
>> copy_page_sse2 (in copy_page.S) in our code base and available (by default)
>> for x86_64. Is it a bad idea to use that ?
> 
> Never mind about copy_page_sse2 ! That function name is misleading.

Why - it is code that's dependent on SSE2 to be available. Note it
doesn't have 'xmm' in its name - that indeed would be misleading.

> But, still ... I need a copy_page routine and was planning to use sse.
> Is that not fine ?

You can do so if you feel like saving/restoring all necessary XMM
state isn't going to eat up all of the performance win...

Jan


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