Avi Kivity wrote: > Aurelien Jarno wrote: >> >>> 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 >> >> > > I'm guessing this is due to the glibc aio implementation, which uses > threads instead of true aio. The threads may cause the vcpu to migrate > frequently from one code to another. > > There are two possible solutions: > > - use native aio from http://www.bullopensource.org/posix/. I think > the aio signal patches are not yet in, so this may not work. > - teach the scheduler about the cost of migrating vcpus > The first approach will solve itself eventually, though slowly if the > current slow rate of aio merging continues. We'll have to do the second. >
if you prefer the first one, Sébastien will release very soon aio patches for
2.6.20 with an up-to-date libposix-aio.
[advertising] Keep an eye on the bullopensource website. [/advertising]
:-P
Regards,
Laurent
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