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

[Hongkaixing <hongkaixing@huawei.com>]

Oh, sorry, this patch is sent in hurry, the whole version is sent out follow this one. 

According to our analysis, the old page in method spends much time in xc_map_foreign_pages, so we introduce a direct way to trigger page in.  This is the point.
After our new page-in method is applied, a new array can speed up page in significantly.

Result shows the page-in speed can reach the hard disk's limit, above 120M/s



> -----邮件原件-----
> 发件人: Olaf Hering [mailto:olaf@aepfle.de]
> 发送时间: 2012年1月6日 4:59
> 收件人: hongkaixing@huawei.com
> 抄送: xen-devel@lists.xensource.com
> 主题: Re: [PATCH] xenpaging:add a new array to speed up page-in in xenpaging
> 
> On Thu, Jan 05, hongkaixing@huawei.com wrote:
> 
> > # HG changeset patch
> > # User hongkaixing<hongkaixing@huawei.com>
> > # Date 1325149704 -28800
> > # Node ID 052727b8165ce6e05002184ae894096214c8b537
> > # Parent  54a5e994a241a506900ee0e197bb42e5f1d8e759
> > xenpaging:add a new array to speed up page-in in xenpaging
> >
> > This patch adds a new array named page_out_index to reserve the victim's
> index.
> > When page in a page,it has to go through a for loop from 0 to num_pages to
> find
> > the right page to read,and it costs much time in this loop.After adding the
> > page_out_index array,it just reads the arrry to get the right page,and saves
> much time.
> >
> > The following is a xenpaging test on suse11-64 with 4G memories.
> >
> > Nums of page_out pages	Page out time	Page in time(in unstable code)
> Page in time(apply this patch)
> > 512M(131072)		    2.6s		           540s
> 530s
> > 2G(524288)		    15.5s		           2088s
> 2055s
> 
> Thanks for your work on this.
> 
> 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.
> 
> Wether an extra array is needed, we have to decide as it costs some
> runtime memory. I was thinking already about better bitop functions,
> like xc_find_next_bit_set and similar, just what xenpaging needs, to
> remove the test bits one-by-one.
> 
> As for the new page-in op, there was some offline discussion about doing
> page-in/page-out differently. If these ideas make into xen-unstable most
> of domctls will disappear, and also the mmap to trigger page-in is not
> needed anymore.
> 
> Olaf


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