From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36819) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TRMOJ-0006cx-9f for qemu-devel@nongnu.org; Thu, 25 Oct 2012 08:18:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TRMOC-0000Sw-Lg for qemu-devel@nongnu.org; Thu, 25 Oct 2012 08:18:27 -0400 Received: from mail.profihost.ag ([85.158.179.208]:36942) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TRMOC-0000Sf-Bh for qemu-devel@nongnu.org; Thu, 25 Oct 2012 08:18:20 -0400 Message-ID: <50892E08.5090404@profihost.ag> Date: Thu, 25 Oct 2012 14:18:16 +0200 From: Stefan Priebe - Profihost AG MIME-Version: 1.0 References: <5088F46D.6080605@profihost.ag> <508909F4.8020100@redhat.com> <508915DE.5080509@profihost.ag> <508924E1.3@redhat.com> In-Reply-To: <508924E1.3@redhat.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] slow xbzrle List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Orit Wasserman Cc: qemu-devel Am 25.10.2012 13:39, schrieb Orit Wasserman: > 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. 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 Greets, Stefan