On Thu, Nov 21, 2013 at 09:01:39AM +0200, Michael S. Tsirkin wrote: > On Thu, Nov 21, 2013 at 03:45:28AM +0000, Zhanghaoyu (A) wrote: > > Hi, all > > > > What's the difference of the linux guest kernel parameter idle=<poll/mwait/halt/nomwait>, especially in performance? > > > > Taking the performance into account, which one is best? > > > > In my opinion, if the number of all VMs' vcpus is far more than that of pcpus, e.g. SPECVirt test, idle=halt is better for server's total throughput, > > otherwise, e.g. in some CT scenario, the number of total vcpus is not greater than that of pcpus, idle=poll is better for server's total throughput, > > because of less latency and VMEXIT. > > Makes sense overall. > > > linux-3.9 and above, idle=mwait is not recommended. > > > > Thanks, > > Zhang Haoyu > > Does it actually have effect? I didn't think it would. mwait instruction is never exposed to a guest. With idle=mwait is will likely fall back to halt silently. -- Gleb. -- 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
