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[Xen-devel] poor I/O performance on domU

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] poor I/O performance on domU
From: Jan Kundrát <jan.kundrat@xxxxxx>
Date: 2005年1月13日 17:06:48 +0100
Delivery-date: 2005年1月13日 17:22:46 +0000
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Hi,
comparing disk I/O performance of domain0 running gentoo and unprivileged domain with ttylinux (tried multiple times, results differ in ~ 1sec range):
In domain0:
zirafa ~ # time dd if=/dev/hda of=/dev/null bs=1M count=500
500+0 records in
500+0 records out
real 0m27.344s
user 0m0.000s
sys 0m2.280s
zirafa ~ # hdparm -t /dev/hda
/dev/hda:
 Timing buffered disk reads: 56 MB in 3.03 seconds = 18.48 MB/sec
-----------------------------
And for unprivileged domains:
root@tiny ~ # time dd if=/dev/sdb1 of=/dev/null bs=1M count=500
500+0 records in
500+0 records out
real 0m41.962s
user 0m0.010s
sys 0m1.920s
root@tiny ~ # hdparm -t /dev/sdb1
/dev/sdb1:
 Timing buffered disk reads: 64 MB in 5.32 seconds = 12.03 MB/sec
ioctl 00001261 not supported by Xen blkdev
hdparm: BLKFLSBUF: Function not implemented
ioctl 0000031f not supported by Xen blkdev
hdparm: HDIO_DRIVE_CMD: Function not implemented
I've tried exporting /dev/hda as /dev/sdb, /dev/sdb1 and /dev/hda, all of them in read-only mode. Results look very similar, only `hdparm -t /dev/hda` from domainU complains bit more:
root@tiny ~ # hdparm -t /dev/hda
/dev/hda:
 Timing buffered disk reads: 64 MB in 5.38 seconds = 11.90 MB/sec
ioctl 00001261 not supported by Xen blkdev
hdparm: BLKFLSBUF: Function not implemented
ioctl 0000031f not supported by Xen blkdev
hdparm: HDIO_DRIVE_CMD: Function not implemented
[XEN:vbd_update:drivers/xen/blkfront/blkfront.c:194] >
[XEN:vbd_update:drivers/xen/blkfront/blkfront.c:195] <
I'm using some older version of Xen/2, compiled on 14 Nov 2004, machine is celeron/466 with 256MB of RAM, 64 for dom0.
ttylinux.conf:
kernel = "/boot/vmlinuz-2.6.9-xenU"
memory = 64
name = "ttylinux"
nics = 1
ip = "10.18.6.10"
disk = ['file:/home/storage/ttylinux-xen,sda1,r','phy:hda,hda,r']
root = "/dev/sda1 ro"
ttylinux's rootfs is exported from ext3 fs via loopback device, could it be the cause of troubles?
-jkt
--
cd /local/pub && more beer > /dev/mouth
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