Date: Sun, 7 Dec 2008 19:19:26 +0100 (CET) From: Juergen Lock <nox@jelal.kn-bremen.de> To: anthony@codemonkey.ws Cc: freebsd-emulation@FreeBSD.org, qemu-devel@nongnu.org Subject: Re: [Qemu-devel] testing qemu svn r5890 on FreeBSD - virtio, and a patch enabling -clock dynticks Message-ID: <200812071819.mB7IJQOT062178@saturn.kn-bremen.de> In-Reply-To: <493B35AB.1050301@codemonkey.ws> References: <20081206220906.GA34210@saturn.kn-bremen.de>
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In article <493B35AB.1050301@codemonkey.ws> you write: >Juergen Lock wrote: >> Hi! >> >> Jung-uk Kim sent me a patch to enable -clock dynticks on FreeBSD hosts >> (the configure check is mine, only FreeBSD >= 7.x has posix timers that >> this uses), I'll append it below. >> >> This is the experimental qemu-devel port update I used: >> http://people.freebsd.org/~nox/qemu/qemu-devel-20081206.patch >> As already mentioned I had to add a missing `#include <sys/uio.h>' >> (files/patch-qemu-common.h), as also posted here: >> http://lists.gnu.org/archive/html/qemu-devel/2008-12/msg00216.html >> >> I only had one (type of) guest that actually had virtio drivers (three >> versions of sidux isos), and the speed difference between virtio-blk and >> scsi was small. (I tested dd bs=64k count=500 </dev/vda >/dev/null and >> similar with a raw image, both scsi and virtio were always faster than ide.) >> I noted tho that even virtio there was not half as fast as ide (and scsi) >> on KNOPPIX_V5.3.1DVD-2008-03-26-EN.iso, so either overhead has increased >> greatly from 2.6.24.4 to 2.6.26, or this has something to do with >> the sidux kernel using CONFIG_NO_HZ and the Knoppix one (apparently) not >> and qemu (possibly, I also suspected that with the usb slowness) not >> handling CONFIG_NO_HZ guests too well. scsi on a FreeBSD >> 7.1-BETA-i386-livefs.iso guest btw was even yet (noticeably) faster than >> on the Knoppix iso. It will be interesting how virtio-net will fare once >> that gets committed... >> > >I don't have much experience with perf benchmarking and TCG. TCG may >has interesting side effects. For instance, it's more expensive to do >things in the guest instead of the host so the emulation overhead of >IDE/SCSI shouldn't matter much. > Actually most of those tests were with -kernel-kqemu sice that is what I usually run linux guests with. >A straight dd test is not the best test BTW. If you want to measure >performance, you should use O_DIRECT in the guest (iflag=direct) Hmm, how many guest processes will use that? Or is that what fses end up doing when the guest does things like, say, cp'ing files around? > and >probably O_DIRECT in the host (cache=none). Ok, will do next time... Thanx, Juergen
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