On 02/28/2012 03:20 PM, Peter Lieven wrote: > On 28.02.2012 14:16, Avi Kivity wrote: >> On 02/24/2012 08:41 AM, Stefan Hajnoczi wrote: >>>> I dont think that it is cpu intense. All user pages are zeroed >>>> anyway, but at allocation time it shouldnt be a big difference in >>>> terms of cpu power. >>> It's easy to find a scenario where eagerly zeroing pages is wasteful. >>> Imagine a process that uses all of physical memory. Once it >>> terminates the system is going to run processes that only use a small >>> set of pages. It's pointless zeroing all those pages if we're not >>> going to use them anymore. >> In the long term, we will use them, except if the guest is completely >> idle. >> >> The scenario in which zeroing is expensive is when the page is refilled >> through DMA. In that case the zeroing was wasted. This is a pretty >> common scenario in pagecache intensive workloads. >> > Avi, what do you think of the proposal to give the guest vm a hint > that the host is running ksm? In that case the administrator > has already chosen that saving physical memory is more important > than performance to him? It makes some sense. Perhaps through the balloon device, a flag that indicates that voluntary ballooning will be gratefully accepted. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
