On 9/30/2010 2:13 AM, Stefan Hajnoczi wrote:
On Thu, Sep 30, 2010 at 1:50 AM, Venkateswararao Jujjuri (JV)
<jv...@linux.vnet.ibm.com> wrote:
Code: Mainline QEMU (git://git.qemu.org/qemu.git)
Machine: LS21 blade.
Disk: Local disk through VirtIO.
Did not select any cache option. Defaulting to writethrough.
Command tested:
3 parallel instances of : dd if=/dev/zero of=/pmnt/my_pw bs=4k count=100000
QEMU with smp=1
19.3 MB/s + 19.2 MB/s + 18.6 MB/s = 57.1 MB/s
QEMU with smp=4
15.3 MB/s + 14.1 MB/s + 13.6 MB/s = 43.0 MB/s
Is this expected?
Did you configure with --enable-io-thread?
Yes I did.
Also, try using dd oflag=direct to eliminate effects introduced by the
guest page cache and really hit the disk.
With oflag=direct , I see no difference and the throughput is so slow and I
would not
expect to see any difference.
It is 225 kb/s for each thread either with smp=1 or with smp=4.
- JV
Stefan
