So, after this summary here are my measurement results: Host environment:
Lenovo X 61 Tablet with Core 2 Duo @ 1.6 GHz, $ GB RAM and a Hitachi HTE 320GB HDD @ 7200rpm debian testing amd64, all partitions formatted with ext4. Guest environment: debian testing amd64, all partitions formatted with ext4. kvm command: kvm -drive file=/home/virtual/KVM/debian.ovl,index=0,media=disk,cache=writeback -k de -m 1G -monitor stdio -net nic,model=virtio,macaddr=52:54:00:12:34:57 -net user -rtc base=localtime -smp 2 -usb -usbdevice tablet -vga std -vnc :4 testcommand: time dd if=/dev/zero of=/root/zero.img bs=1024k count=1024 qemu-kvm_0.12.4+dfsg1_amd64.deb cache=writeback real 0m24.837s user 0m 0.008s sys 0m 9.997s cache=writethrough real 3m11.935s user 0m 0.024s sys 0m10.153s cache=none real 0m40.837s user 0m 0.012s sys 0m10.713s qemu-kvm_0.12.5+dfsg1_amd64.deb cache=writeback real 2m26.086s user 0m 0.020s sys 0m10.537s cache=writethrough real 3m18.835s user 0m 0.008s sys 0m 9.985s cache=none real 2m22.439s user 0m 0.024s sys 0m10.317s The measurements of the first bugreport were subjective and for my machine you can see that with 0.12.5 changing the cache to writethrough|writeback|none has "nearly" no effect to the write performance. On Wed, 25 Aug 2010 12:11:19 +0400 Michael Tokarev <m...@tls.msk.ru> wrote: > The change in question does _not_ affect writethrough > mode, since there, all writes always were syncronous > anyway. This is despite the information found in > first message that started this bugreport. Alexander > Loob said: > > Changing the cache value to cache=none or writethrough > has no effect to the write performance. > > This is incorrect. Yet again, the change does not > affect the default writethrough cache mode, since > it were syncronous before, and the change is a no-op > for that mode. Note that this is the default cache > mode, so actually the change does not affect most > users.
signature.asc
Description: PGP signature
