Re: [Xen-devel] [PATCH] xenpaging:add a new array to speed up page-in in xenpaging

[Hongkaixing <hongkaixing@xxxxxxxxxx>]

> -----Original Message-----
> From: Olaf Hering [mailto:olaf@xxxxxxxxx]
> Sent: Friday, January 06, 2012 9:08 PM
> To: hongkaixing@xxxxxxxxxx
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH] xenpaging:add a new array to speed up page-in in 
> xenpaging
> 
> On Thu, Jan 05, Olaf Hering wrote:
> 
> > Is the page-out time for 512M really that fast? For me page-out is still
> > really slow even when the pagefile is in tmpfs. It takes several
> > minutes, I get around 4MB/s. page-in is around 20MB/s.
> 
> Wait, the slow page-out is due to the poll() timeout in
> xenpaging_wait_for_event_or_timeout(). This can be fixed with some sort
> of dynamic timeout while there is still something to page-out.

   I don't think so. Our approach still use 100ms in poll(), Using 10ms seems 
no significant change.

   In my opinion, In order to improve speed , 2 points are necessary:
   1. put page-in request fast
   2. request should be in disk order. Especially for a large swap file.


> 
> Olaf


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