Re: [Xen-users] Exporting a PCI Device

[Jan Kalcic <jandot@xxxxxxxxxxxxxx>]

Joris Dobbelsteen wrote:
>> -----Original Message-----
>> From: Jan Kalcic [mailto:jandot@xxxxxxxxxxxxxx] 
>> Sent: Monday, 18 February 2008 23:44
>> To: Joris Dobbelsteen
>> Cc: deshantm@xxxxxxxxx; xen-users@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: [Xen-users] Exporting a PCI Device
>>
>>     
> [snip]
>   
>> I did some test and actually it's quite slow both in reading 
>> and in writing. Roughly 50% as Block Device attacched to the domU.
>> It reduces complexity but too much is lost in performance.
>>     
>
> For some odd reason I'm seeing a similar things on my box with attached
> RAID-0 & LVM. The domU only reaches 50%. I don't know the cause, I only
> heared comments that it had todo with LVM oddities that RAID seemed to
> aggrivate. Nevertheless the dom0 reaches full speed.
>
> Coincidence or a sign of deeper trouble?
>
> My setup is just some standard (cheap) SATA disks, it's a personal
> system. It does run Xen 3.1.2, the 2.6.20 kernel on the domU and the
> Debian Etch 2.6.18 kernels on the guests. Tests where with Bonnie++
> (that's part of debian etch).
>
> To rule out the virtual block device playing tricks I would try to see
> what happens with a slower disk on the SAN and even with a local disk
> (in the system itself).
>
> - Joris
>
>
>   
Hi Joris,

I did some test on the local disk (software RAID) of another system just
to have an idea about performance. There is a bit lost in performance,
dom0 tends to be a little quicker even if the difference is not so big
to be problematic. Differently was on the other system with SAN which I
could not test. I'll do soon and I'll let you know. The following is the
output of the test I did.

What do you mean when you say "deeper trouble"? Do you refer to Xen code
or something about the infrastructure configuration?

Thanks,
Jan


domU

# dd if=/dev/zero of=/mnt/test count=1000 bs=1M
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 18.7752 seconds, 55.8 MB/s

1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 12.395 seconds, 84.6 MB/s

1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 18.1577 seconds, 57.7 MB/s


# hdparm -t /dev/sdd1 (three times)

/dev/sdd1:
 Timing buffered disk reads:  116 MB in  3.00 seconds =  38.62 MB/sec

/dev/sdd1:
 Timing buffered disk reads:  156 MB in  3.01 seconds =  51.80 MB/sec

/dev/sdd1:
 Timing buffered disk reads:  148 MB in  3.03 seconds =  48.85 MB/sec
-------------------------------------------------------------
dom0

# dd if=/dev/zero of=/data/test count=1000 bs=1M (three times)
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 13.2577 seconds, 79.1 MB/s

1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 18.3124 seconds, 57.3 MB/s

1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 12.244 seconds, 85.6 MB/s

# hdparm -t /dev/md3

/dev/md3:
 Timing buffered disk reads:  164 MB in  3.02 seconds =  54.37 MB/sec

/dev/md3:
 Timing buffered disk reads:  172 MB in  3.01 seconds =  57.21 MB/sec

/dev/md3:
 Timing buffered disk reads:  180 MB in  3.01 seconds =  59.85 MB/sec
                                                         



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