Re: [Qemu-devel] slow xbzrle

[Stefan Priebe]

Am 25.10.2012 15:15, schrieb Orit Wasserman:
> > > Looks like a lot of cache miss, you can try increasing the cache size 
> > > (migrate_set_cache_size).
> > > But you should remember that for an idle guest XBZRLE is wasteful,
> > > it is useful for workload that changes the same memory pages frequently.
> >
> > sure here are some values from a loaded VM (20% cpu load with MySQL) - with an 
> > increased cache size does not look much better:
> >
> > Oct 25 14:16:39 migration xbzrle cachesize: 536870912 transferred 0 pages 0 
> > cachemiss 159634 overflow 0
> > Oct 25 14:16:41 migration xbzrle cachesize: 536870912 transferred 0 pages 0 
> > cachemiss 173631 overflow 0
> > Oct 25 14:16:43 migration xbzrle cachesize: 536870912 transferred 0 pages 0 
> > cachemiss 187627 overflow 0
> > Oct 25 14:16:45 migration xbzrle cachesize: 536870912 transferred 0 pages 0 
> > cachemiss 201624 overflow 0
> It looks like the cache got smaller 1073741824 > 536870912 ...
> try 2G cache size
> Orit

Here from another VM running into overflow setting cache size to 50% of mem:
Oct 25 22:43:57 migration xbzrle cachesize: 2147483648 transferred 
36294204 pages 520357 cachemiss 392074 overflow 947

Oct 25 22:44:31 migration xbzrle cachesize: 2147483648 transferred 
45438419 pages 653350 cachemiss 392091 overflow 1024

Oct 25 22:44:55 migration xbzrle cachesize: 2147483648 transferred 
51310028 pages 742877 cachemiss 392096 overflow 1054

Greets,
Stefan