On 11/02/2011 06:02 PM, Andrea Arcangeli wrote: > Hi Avi, > > On Wed, Nov 02, 2011 at 05:44:50PM +0200, Avi Kivity wrote: > > If you look at cleancache, then it addresses this concern - it extends > > pagecache through host memory. When dropping a page from the tail of > > the LRU it first goes into tmem, and when reading in a page from disk > > you first try to read it from tmem. However in many workloads, > > cleancache is actually detrimental. If you have a lot of cache misses, > > then every one of them causes a pointless vmexit; considering that > > servers today can chew hundreds of megabytes per second, this adds up. > > On the other side, if you have a use-once workload, then every page that > > falls of the tail of the LRU causes a vmexit and a pointless page copy. > > I also think it's bad design for Virt usage, but hey, without this > they can't even run with cache=writeback/writethrough and they're > forced to cache=off, and then they claim specvirt is marketing, so for > Xen it's better than nothing I guess. Surely Xen can use the pagecache, it uses Linux for I/O just like kvm. > I'm trying right now to evaluate it as a pure zcache host side > optimization. zcache style usage is fine. It's purely internal so no ABI constraints, and no hypercalls either. It's still synchronous though so RAMster like approaches will not work well. <snip> -- error compiling committee.c: too many arguments to function -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>