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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Jan also added a copy_page hypercall, so he may have been optimising for
that, since I guess the Novell kernels must use it.

 -- Keir

On 16/07/2010 00:36, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> I wasn't sure about that... Jan's patch to speed up
> copy_page (by 12%) went in before tmem was in-tree,
> so I assumed otherwise.  Clearly my interest is for
> tmem, especially if 2x-4x improvement is possible,
> but if there really is no significant advantage for
> non-tmem code, I will put it on my list... for sometime
> in the next century when I am a good x86 assembly
> programmer :-)
> 
>> -----Original Message-----
>> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
>> Sent: Thursday, July 15, 2010 3:35 PM
>> To: Dan Magenheimer; Jan Beulich
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: Even faster page copy for Xen?
>> 
>> It has to be said, possibly tmem excepted, there is very little page
>> copying
>> in Xen.
>> 
>>  -- Keir
>> 
>> On 15/07/2010 19:15, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>
>> wrote:
>> 
>>> Hi Jan, Keir --
>>> 
>>> My x86 assembly skills are much too poor to carefully evaluate
>>> and, if of value, implement this in Xen but given your previous
>>> interest, such as:
>>> 
>>> http://xenbits.xensource.com/xen-unstable.hg?rev/8de4b4e9a435
>>> 
>>> the following might be worth looking at.
>>> 
>>> Intel has just posted memcpy improvements for glibc for recent
>>> popular Intel processor families here:
>>> 
>>> http://article.gmane.org/gmane.comp.lib.glibc.alpha/15278
>>> 
>>> The preface to the above patch looks very enticing...
>>> 
>>> Semi-related, I wonder if you know, if there were a
>>> "copy_page_from_other_node()" to be used if the
>>> caller is fairly sure that the page is being copied
>>> between nodes, could this be made significantly faster
>>> than a normal copy_page()?
>>> 
>>> Thanks,
>>> Dan
>> 
>> 



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