On Thu, Nov 19, 2015 at 11:16:22AM +0300, Vasiliy Tolstov wrote: > I'm test virtio-scsi on various kernels (with and without scsi-mq) > with deadline io scheduler (best performance). I'm test with lvm thin > volume and with sheepdog storage. Data goes to ssd that have on host > system is about 30K iops. > When i'm test via fio > [randrw] > blocksize=4k > filename=/dev/sdb > rw=randrw > direct=1 > buffered=0 > ioengine=libaio > iodepth=32 > group_reporting > numjobs=10 > runtime=600 > > > I'm always stuck at 11K-12K iops with sheepdog or with lvm. > When i'm switch to virtio-blk and enable data-plane i'm get around 16K iops. > I'm try to enable virtio-scsi-data-plane but may be miss something > (get around 13K iops) > I'm use libvirt 1.2.16 and qemu 2.4.1 > > What can i do to get near 20K-25K iops? > > (qemu testing drive have cache=none io=native)
If the workload is just fio to a single disk then dataplane (-object
iothread) may not help massively. The scalability of dataplane kicks in
when doing many different types of I/O or accessing many disks. If you
have just 1 disk and the VM is only running fio, then dataplane simply
shifts the I/O work from the QEMU main loop to a dedicated thread. This
results in an improvement but it may not be very dramatic for a single
disk.
You can get better aio=native performance with qemu.git/master. Please
see commit fc73548e444ae3239f6cef44a5200b5d2c3e85d1 ("virtio-blk: use
blk_io_plug/unplug for Linux AIO batching").
Stefan
signature.asc
Description: PGP signature
