On 10/25/2012 12:35 PM, Stefan Priebe - Profihost AG wrote:
Am 25.10.2012 11:44, schrieb Orit Wasserman:
Is this known or is something wrong?
My guess this workload migrates fine without XBZRLE so it is not the speed or
downtime :).
it could be that the cache size is too small resulting with a lot of cache
misses which means
XBZRLE makes things worse and just uses CPU to maintain the cache.
Other option is that this workload changes the pages too much which can result
with a lot of over flows
which result in XBZRLE to waste CPU scanning the pages.
As this is idle mysql my guess it the first scenario.
Can you send the cache size, cache miss and overflow (from 'info migrate')?
Example got from a log file (it's the info from info migrate just in another
format):
migration xbzrle
cachesize: 1073741824
transferred 0
pages 0
cachemiss 1315374
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.