[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] 4.2.1: Poor write performance for DomU.



On Wed, Feb 20, 2013 at 10:08:58PM +1100, Steven Haigh wrote:
> On 20/02/2013 10:06 PM, Andrew Cooper wrote:
> >On 20/02/13 10:12, Jan Beulich wrote:
> >>>>>On 20.02.13 at 10:49, Steven Haigh <netwiz@xxxxxxxxx> wrote:
> >>>My build of Xen 4.2.1 also has all of the recent security advisories
> >>>patched as well. Although it is interesting to note that downgrading to
> >>>Xen 4.1.2 made no difference to write speeds.
> >>Not surprising at all, considering that the hypervisor is only a passive
> >>library for all PV I/O purposes. You're likely hunting for a kernel side
> >>regression (and hence the mentioning of the hypervisor version as
> >>the main factor in the subject is probably misleading).
> >>
> >>Jan
> >
> >Further to this, do try to verify if your disk driver has changed
> >recently to use >0 order page allocations for DMA.  If it has, then
> >speed will be much slower as there will now be the swiotlb cpu-copy
> >overhead.
> 
> Any hints on how to do this? ;)
> 
> The kernel modules in use for my SATA drives are ahci and sata_mv.
> There are 6 drives in total on the system.
> 
> sda + sdb = RAID1
> sd[c-f] = RAID6
> 
> sda, sdb, sdc and sdd are on the onboard SATA controller (ahci)
> sde, sdf are on the sata_mv 4x PCIe controller.
> 

Can you try using only the disks on the ahci controller?

sata_mv is known to be buggy and problematic.. 
I'm not sure if that's the case here, but if you're able to easily 
try using only ahci, it's worth a shot. 

-- Pasi


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.