Re: [Qemu-devel] [RFC][PATCH 6/9] migration: use XBZRLE only after bulk stage

[Eric Blake]

On 03/12/2013 09:51 AM, Peter Lieven wrote:
> at the beginning of migration all pages are marked dirty and
> in the first round a bulk migration of all pages is performed.
> 
> currently all these pages are copied to the page cache regardless
> if there are frequently updated or not. this doesn't make sense
> since most of these pages are never transferred again.
> 
> this patch changes the XBZRLE transfer to only be used after
> the bulk stage has been completed. that means a page is added
> to the page cache the second time it is transferred and XBZRLE
> can benefit from the third time of transfer.
> 
> since the page cache is likely smaller than the number of pages
> its also likely that in the second round the page is missing in the
> cache due to collisions in the bulk phase.
> 
> on the other hand a lot of unneccssary mallocs, memdups and frees

s/unneccssary/unnecessary/

> are saved.

Earlier, I asked you for some benchmark numbers, and you provided some.
 Mentioning them in the commit message will make an even stronger
argument for including this patch.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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