>Avi Kivity wrote: >> Nakajima, Jun wrote: >>> I compared the performance on Xen and KVM for kernel build using the >>> same guest image. Looks like KVM was (kvm-17) three times slower as >>> far as we tested, and that high load of qemu was one of the >>> symptoms. We are looking at the shadow code, but the load of qemu >>> looks very high. I remember we had similar problems in Xen before, >>> but those were fixed. Someone should take a look at the qemu side. >>> >> >> I'd expect the following issues to dominate: >> >> - the shadow cache is quite small at 256 pages. Increasing it may >> increase performance. > >Yes, we are aware of this. > >> >> - we haven't yet taught the scheduler that migrating vcpus is >> expensive due to the IPI needed to fetch the vmcs. Maybe running >> with 'taskset 1' would help >> >> - shadow eviction policy is FIFO, not LRU, which probably causes many >> page faults. > >This may explain that the performance gets worse as we repeat kernel >build, at least, the second run is slower than the first one. > >> >> Running kvm_stat can help show what's going on. > >Thanks for the good insights. We'll come back with some analysis.
Maybe you can come up with a patch ;) If you touch those areas anyway and run several benchmarks, writing a small piece of code is neglectable effort. > >Jun >--- >Intel Open Source Technology Center ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
