Re: Poor disk performance in NetBSD DomU, again

[Yi Qiao <qiaoy%qiaoy.info@localhost>]

On Tue, May 13, 2014 at 1:33 PM, Manuel Bouyer 
<bouyer%antioche.eu.org@localhost> wrote:
> On Tue, May 13, 2014 at 01:29:23PM -0400, Yi Qiao wrote:
>> Hi Manuel
>>
>>   Sorry about that. It's all PV guests. And I don't think partition
>> alignments is the dominating issue here since after each experiment, I
>
> it can, depending on how the virtual disk is partitionned in the guest.

I see. For the NetBSD installs, I simply partitioned xvda into / with
9728M and swap with 512M. For the FreeBSD install, I accepted the
default partition scheme, which I think is a very small boot partition
at the beginning, 9G ish in the middle for /, and 512M as swap. For
Ubuntu, I let the installer create it's own lvm.

The only straightforward way I can think to test the theory right now
is to change the order of the root and swap partitions during a NetBSD
install. However since the swap is only 512M, I doubt it will make a
noticeable difference.

>
>> remove the lvm volume for that guest, and create a new one for the
>> next guest.
>>
>>   I also did some more experiment with HVM guests, and here are the
>> results (all with NetBSD Dom0)
>>
>>   NetBSD: 61.66 MB/s (write); 73.69 MB/s (read)
>>   FreeBSD-9.2: 98.61 MB/s (write); 103.81 MB/s (read)
>>   OpenBSD-5.5: 24.91 MB/s (write); 59.96 MB/s (read)
>>   Ubuntu 14.04: 129 MB/s (write); 131 MB/s (read)
>>
>> It's interesting to see that NetBSD HVM DomU actually out-performed PV
>> DomU,
>
> that's strange indeed

It feels almost like a filesystem / harddrive caching issue to me. On
a separate test, in which I was trying to optimize NFS performance,
the write speed is around 20MB/s to a Ubuntu server over my gigabit
ethernet. But as soon as I changed the server to be async NFS, the
speed jumped to 100MB/s

>
>> but still lagging behind FreeBSD and Ubuntu.
>
> that's not surprising, as NetBSD HVM guests lacks PV drivers.
>
> --
> Manuel Bouyer <bouyer%antioche.eu.org@localhost>
>      NetBSD: 26 ans d'experience feront toujours la difference
> --