[Xen-users] Low PV hard disk performance

[Tony Hoyle <tmh@xxxxxxxxxxxx>]

Hi,

I just ran an hdparm on a PV domain after I experienced severe I/O
issues on a network share.

Basically Xen 3.1 domU disk performance is about 1/15th that of the dom0
and really quite poor.

dom0:
/dev/vg0/sisko2-disk:
Timing cached reads:   5870 MB in  1.99 seconds = 2942.59 MB/sec
Timing buffered disk reads:  184 MB in  3.01 seconds =  61.22 MB/sec

domU (same disk):
/dev/sda1:
Timing cached reads:   6392 MB in  1.99 seconds = 3204.37 MB/sec
Timing buffered disk reads:   16 MB in  3.50 seconds =   4.57 MB/sec

The network I/O is simplarly afflicted, and runs 25 times worse than native:

dom0->real machine:
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 8192  16384  16384    10.00     830.36

domu->real machine:
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 8192  16384  16384    10.15      30.98

dom0->domu:

Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

87380  16384  16384    10.02      35.85

domu->domu:
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

87380  16384  16384    10.01      33.72

As is clear both network and disk performance are simply unnaceptable,
even for test machines.  I've tried pretty much every tweak that I can
find and can't make any difference to it.  Currently the only thing keeping
vmware server away is its linux version is 32bit only..

Any ideas?

Tony

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