[Qemu-devel] poor virtio-scsi performance (fio testing)

[Qemu-devel] poor virtio-scsi performance (fio testing)

[Vasiliy Tolstov]

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)

-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Stefan Hajnoczi]

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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

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Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Vasiliy Tolstov]

2015-11-25 12:35 GMT+03:00 Stefan Hajnoczi <stefanha@gmail.com>:
> 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").


Thanks Stefan! Does this patch only for virtio-blk or it can increase
iops for virtio-scsi ?

-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Fam Zheng]

On Wed, 11/25 13:10, Vasiliy Tolstov wrote:
> 2015-11-25 12:35 GMT+03:00 Stefan Hajnoczi <stefanha@gmail.com>:
> > 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").
> 
> 
> Thanks Stefan! Does this patch only for virtio-blk or it can increase
> iops for virtio-scsi ?
> 

The patch was for virtio-blk but qemu.git/master also has another patch for
virtio-scsi (5170f40 virtio-scsi: Call bdrv_io_plug/bdrv_io_unplug in cmd
request handling).

On the other hand it would be helpful to compare the difference between
virtio-blk and virtio-scsi in your environment. Could you do that?

Fam

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Alexandre DERUMIER]

Maybe could you try to create 2 disk in your vm, each with 1 dedicated iothread,

then try to run fio on both disk at the same time, and see if performance improve.


But maybe they are some write overhead with lvmthin (because of copy on write) and sheepdog.

Do you have tried with classic lvm or raw file ?


----- Mail original -----
De: "Vasiliy Tolstov" <v.tolstov@selfip.ru>
À: "qemu-devel" <qemu-devel@nongnu.org>
Envoyé: Jeudi 19 Novembre 2015 09:16:22
Objet: [Qemu-devel] poor virtio-scsi performance (fio testing)

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) 

-- 
Vasiliy Tolstov, 
e-mail: v.tolstov@selfip.ru 

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Vasiliy Tolstov]

2015-11-25 13:08 GMT+03:00 Alexandre DERUMIER <aderumier@odiso.com>:
> Maybe could you try to create 2 disk in your vm, each with 1 dedicated iothread,
>
> then try to run fio on both disk at the same time, and see if performance improve.
>

Thats fine, but by default i have only one disk inside vm, so i prefer
increase single disk speed.

>
> But maybe they are some write overhead with lvmthin (because of copy on write) and sheepdog.
>
> Do you have tried with classic lvm or raw file ?

I'm try with classic lvm - sometimes i get more iops, but stable
results is the same =)


-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Alexandre DERUMIER]

>>I'm try with classic lvm - sometimes i get more iops, but stable
results is the same =)

I have tested with a raw file, qemu 2.4 + virtio-scsi (without iothread), I'm around 25k iops
with an intel ssd 3500. (host cpu are xeon v3 3,1ghz)


randrw: (g=0): rw=randrw, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=32
...
fio-2.1.11
Starting 10 processes
Jobs: 4 (f=3): [m(2),_(3),m(1),_(3),m(1)] [100.0% done] [96211KB/96639KB/0KB /s] [24.6K/24.2K/0 iops] [eta 00m:00s]
randrw: (groupid=0, jobs=10): err= 0: pid=25662: Wed Nov 25 11:25:22 2015
  read : io=5124.7MB, bw=97083KB/s, iops=24270, runt= 54047msec
    slat (usec): min=1, max=34577, avg=181.90, stdev=739.20
    clat (usec): min=177, max=49641, avg=6511.31, stdev=3176.16
     lat (usec): min=185, max=52810, avg=6693.55, stdev=3247.36
    clat percentiles (usec):
     |  1.00th=[ 1704],  5.00th=[ 2576], 10.00th=[ 3184], 20.00th=[ 4016],
     | 30.00th=[ 4704], 40.00th=[ 5344], 50.00th=[ 5984], 60.00th=[ 6688],
     | 70.00th=[ 7456], 80.00th=[ 8512], 90.00th=[10304], 95.00th=[12224],
     | 99.00th=[17024], 99.50th=[19584], 99.90th=[26240], 99.95th=[29568],
     | 99.99th=[37632]
    bw (KB  /s): min= 6690, max=12432, per=10.02%, avg=9728.49, stdev=796.49
  write: io=5115.1MB, bw=96929KB/s, iops=24232, runt= 54047msec
    slat (usec): min=1, max=37270, avg=188.68, stdev=756.21
    clat (usec): min=98, max=54737, avg=6246.50, stdev=3078.27
     lat (usec): min=109, max=56078, avg=6435.53, stdev=3134.23
    clat percentiles (usec):
     |  1.00th=[ 1960],  5.00th=[ 2640], 10.00th=[ 3120], 20.00th=[ 3856],
     | 30.00th=[ 4512], 40.00th=[ 5088], 50.00th=[ 5664], 60.00th=[ 6304],
     | 70.00th=[ 7072], 80.00th=[ 8160], 90.00th=[ 9920], 95.00th=[11712],
     | 99.00th=[16768], 99.50th=[19328], 99.90th=[26496], 99.95th=[31104],
     | 99.99th=[42752]
    bw (KB  /s): min= 7424, max=12712, per=10.02%, avg=9712.21, stdev=768.32
    lat (usec) : 100=0.01%, 250=0.01%, 500=0.02%, 750=0.03%, 1000=0.05%
    lat (msec) : 2=1.49%, 4=19.18%, 10=68.69%, 20=10.10%, 50=0.45%
    lat (msec) : 100=0.01%
  cpu          : usr=1.28%, sys=8.94%, ctx=329299, majf=0, minf=76
  IO depths    : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=100.0%, >=64=0.0%
     submit    : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
     complete  : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.1%, 64=0.0%, >=64=0.0%
     issued    : total=r=1311760/w=1309680/d=0, short=r=0/w=0/d=0
     latency   : target=0, window=0, percentile=100.00%, depth=32

Run status group 0 (all jobs):
   READ: io=5124.7MB, aggrb=97082KB/s, minb=97082KB/s, maxb=97082KB/s, mint=54047msec, maxt=54047msec
  WRITE: io=5115.1MB, aggrb=96928KB/s, minb=96928KB/s, maxb=96928KB/s, mint=54047msec, maxt=54047msec

Disk stats (read/write):
  sdb: ios=1307835/1305417, merge=2523/2770, ticks=4309296/3954628, in_queue=8274916, util=99.95%


----- Mail original -----
De: "Vasiliy Tolstov" <v.tolstov@selfip.ru>
À: "aderumier" <aderumier@odiso.com>
Cc: "qemu-devel" <qemu-devel@nongnu.org>
Envoyé: Mercredi 25 Novembre 2015 11:12:33
Objet: Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

2015-11-25 13:08 GMT+03:00 Alexandre DERUMIER <aderumier@odiso.com>: 
> Maybe could you try to create 2 disk in your vm, each with 1 dedicated iothread, 
> 
> then try to run fio on both disk at the same time, and see if performance improve. 
> 

Thats fine, but by default i have only one disk inside vm, so i prefer 
increase single disk speed. 

> 
> But maybe they are some write overhead with lvmthin (because of copy on write) and sheepdog. 
> 
> Do you have tried with classic lvm or raw file ? 

I'm try with classic lvm - sometimes i get more iops, but stable 
results is the same =) 


-- 
Vasiliy Tolstov, 
e-mail: v.tolstov@selfip.ru 

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Vasiliy Tolstov]

2015-11-25 13:27 GMT+03:00 Alexandre DERUMIER <aderumier@odiso.com>:
> I have tested with a raw file, qemu 2.4 + virtio-scsi (without iothread), I'm around 25k iops
> with an intel ssd 3500. (host cpu are xeon v3 3,1ghz)


What scheduler you have on host system? May be my default cfq slowdown?

-- 
Vasiliy Tolstov,
e-mail: v.tolstov@selfip.ru

Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

[Alexandre DERUMIER]

>>May be my default cfq slowdown?

Yes ! (in your first mail you said that you use deadline scheduler ?)

cfq don't play well with a lof of current job.

cfq + numjobs=10 : 10000 iops
cfq + numjobs=1 : 25000 iops
deadline + numjobs=1 : 25000 iops
deadline + numjobs=10 : 25000 iops


----- Mail original -----
De: "Vasiliy Tolstov" <v.tolstov@selfip.ru>
À: "aderumier" <aderumier@odiso.com>
Cc: "qemu-devel" <qemu-devel@nongnu.org>
Envoyé: Mercredi 25 Novembre 2015 11:48:11
Objet: Re: [Qemu-devel] poor virtio-scsi performance (fio testing)

2015-11-25 13:27 GMT+03:00 Alexandre DERUMIER <aderumier@odiso.com>: 
> I have tested with a raw file, qemu 2.4 + virtio-scsi (without iothread), I'm around 25k iops 
> with an intel ssd 3500. (host cpu are xeon v3 3,1ghz) 


What scheduler you have on host system? May be my default cfq slowdown? 

-- 
Vasiliy Tolstov, 
e-mail: v.tolstov@selfip.ru