KVM instances have qemu_opts and qemu_extra_opts (see vmadm(1)). These are intended for debugging, and not general use. It's worthwhile to play with these for benchmarking, but I wouldn't run anything production with these set.
-- Brian Bennett Systems Engineer, Cloud Operations, Joyent, Inc. 655 Montgomery St., Suite 1600 | San Francisco | California | 94111 [email protected] <mailto:[email protected]> | www.joyent.com <http://www.joyent.com/> office 415-400-0645 | mobile 619-663-IPv6 > On Apr 27, 2015, at 12:31 AM, Gavin Ang <[email protected]> wrote: > > Hi, > Am trying to optimize the disk I/O performance for KVM guests running on > my SmartOS Host (RAID 10 with 4 disks), 8 physical cores, 100G+ RAM. > > Running this command: time sh -c "dd if=/dev/zero of=ddfile bs=8k > count=250000 && sync"; rm ddfile > > On the Host gives: > real 0m16.051s > user 0m0.186s > sys 0m3.181s > > On a Centos guest gives: > real 0m43.182s > user 0m0.032s > sys 0m1.505s > > - More than 50% degradation on write throughput performance. Been > surfing through many sites, and some suggest using io=native and cache=none > as qemu options to eliminate double caching etc. However, I can’t seem to > find a way to do this. Tried editing the startvm file at /zones/{$UUID}/root > at the option. This is also true of any other image I am running where the > guest io performance is a far cry from the host performance. > > "-drive" "file=/dev/zvol/rdsk > /zones/d0a2fc0f-e623-4423-bcba-b73a56d73c18-disk0,if=virtio,index=0,media=disk,boot=on" > by adding io=native,cache=none to the option, but this file gets overwritten > every time the VM is restarted. Tried putting updating a VM with these > parameters also for the disk, but would not accept this. I know there is an > option called qemu_extra_opts, but don’t think the syntax would be right. BTW > the Centos image above is an image downloaded from Joyent public images. > > The setting "echo zfs_vdev_max_pending/W0t35 | mdb -kw" seemed to give some > improvement on 1 server, but not on another host. > > Any help on this would be much appreciated. > > Thanks, > Gavin > smartos-discuss | Archives > <https://www.listbox.com/member/archive/184463/=now> > <https://www.listbox.com/member/archive/rss/184463/26986985-d0246faa> | > Modify <https://www.listbox.com/member/?&;> Your Subscription > <http://www.listbox.com/>
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