Avi Kivity a écrit : > Aurelien Jarno wrote: >> Avi Kivity a écrit : >> >>> Aurelien Jarno wrote: >>> >>>> The bad news is that kvm-14 seems to be a lot slower than kvm-12 + >>>> modules from kernel 2.6.20. This is the case with a GNU/kFreeBSD guest. >>>> kvm-12 was about 1.5 time faster than qemu + kqemu. kvm-20 is slower >>>> than qemu without kqemu... >>>> >>>> Does anybody have an idea about this performance regression? >>>> >>>> >>> What is your workload? How are you measuring performance? >>> >> Sorry to answer only now, it took me some time to do some more >> measurements and have some numbers. I am simply building a Debian >> package (simulpic) and measuring the build time. Basically the command is: >> >> apt-get source simulpic >> cd simulpic-2005-1-28 >> time debuild -uc us >> >> It surely not a performance index, but I guess it is ok to compare >> performances between version. It is also quite representative of my use >> of the machine. >> > > Real workloads (likr this) are more important than synthetic benchmarks. > >> The guest is Debian GNU/kFreeBSD amd64 (ie FreeBSD kernel + GNU libc). >> It is accessed via ssh, and kvm is started with -nographic, so there is >> no influence of xorg. >> >> I am doing my tests on an Athlon X2 3800+ machine, running a 2.6.20 >> kernel. During all my tests, the machine is not loaded with other tasks >> (except systems tasks), so qemu or kvm have a full core available. Top >> shows that the core is used between 95 and 100% during the whole build >> in all cases. >> >> The tests I have made are presented below. In all cases I have verified >> that the real time correspond to the time of my wall clock, it is >> correct in all case given the resolution of my wall clock (1 s): >> >> qemu >> ---- >> real 3m16.626s >> user 2m22.654s >> sys 0m41.738s >> > > Is this qemu 0.8.2 or qemu 0.9.0?
It's qemu 0.9.0 + kqemu 1.3.0pre11. kqemu is enabled in user mode only (kernel mode does not work well on amd64) >> qemu + kqemu >> ------------ >> real 0m51.529s >> user 0m11.775s >> sys 0m36.215s >> >> kvm 12 + modules from kernel 2.6.20 >> ----------------------------------- >> real 0m30.635s >> user 0m16.357s >> sys 0m8.511s >> >> kvm 12 >> ------ >> real 0m25.357s >> user 0m16.259s >> sys 0m6.496s >> >> kvm 13 >> ------ >> real 0m23.415s >> user 0m15.177s >> sys 0m5.811s >> > > So far so good. Steady improvement. The low system time indicates a > lot of I/O and inefficiency in the qemu device emulation (guest time is > charged as system time). > >> kvm 14 >> ------ >> real 7m47.310s >> user 5m17.359s >> sys 2m3.184s >> >> >> Using kvm 14, the system is clearly not responsive at all. You can see >> that without running a benchmark. >> > > kvm-14 is mostly qemu 0.9.0. Do you get the same results with kvm-14 > -no-kvm? Here are the results: real 3m45.459s user 2m48.581s sys 0m48.585s It's a bit slower than qemu 0.9.0, but a lot faster than kvm 0.9.0 with kvm enable. > What is your disk image file format, or are you using a partition? I am using a raw image file on an ext3 partition. > Do the results change (on kvm-14) if you pin the guest to a core with > 'taskset 1 qemu ...' Bingo. It now works even faster than kvm-13! real 0m22.307s user 0m13.935s sys 0m4.720 > Thank you for taking the time to do real measurements and report the > results clearly. That makes it possible (I hope) to find the cause and > fix it. Thanks for your help! Do you think this problem is fixable? On my final machine, I have a dozen of qemu/kvm running, and when I start them I don't know how they will be used, and so how to pin them on the two cores. -- .''`. Aurelien Jarno | GPG: 1024D/F1BCDB73 : :' : Debian developer | Electrical Engineer `. `' [EMAIL PROTECTED] | [EMAIL PROTECTED] `- people.debian.org/~aurel32 | www.aurel32.net ------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/kvm-devel
