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

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 

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

> -----éäåä-----
> åää: Olaf Hering [mailto:olaf@xxxxxxxxx]
> åéæé: 2012å1æ6æ 4:59
> æää: hongkaixing@xxxxxxxxxx
> æé: xen-devel@xxxxxxxxxxxxxxxxxxx
> äé: Re: [PATCH] xenpaging:add a new array to speed up page-in in xenpaging
> On Thu, Jan 05, hongkaixing@xxxxxxxxxx wrote:
> > # HG changeset patch
> > # User hongkaixing<hongkaixing@xxxxxxxxxx>
> > # 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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