From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: 4.2.1: Poor write performance for DomU. Date: Fri, 8 Mar 2013 15:42:17 -0500 Message-ID: <20130308204217.GA22146@phenom.dumpdata.com> References: <51243089.8020307@crc.id.au> <512488AC.1020702@citrix.com> <51248E23.7060408@crc.id.au> <51249C11.3050800@crc.id.au> <5124AF9F02000078000BFA35@nat28.tlf.novell.com> <5124AE19.2000802@citrix.com> <5124AECA.4060503@crc.id.au> <20130220131846.GJ8912@reaktio.net> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <20130220131846.GJ8912@reaktio.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= Cc: Andrew Cooper , Roger Pau Monne , Steven Haigh , Jan Beulich , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On Wed, Feb 20, 2013 at 03:18:46PM +0200, Pasi K=E4rkk=E4inen wrote: > 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 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 pass= ive > > >>library for all PV I/O purposes. You're likely hunting for a kernel s= ide > > >>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? ;) They are fine. They use the SG DMA API: konrad@phenom:~/linux/drivers/ata$ grep "dma_map" * libata-core.c: n_elem =3D dma_map_sg(ap->dev, qc->sg, qc->n_elem, qc->dma_d= ir); > > = > > 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 =3D RAID1 > > sd[c-f] =3D 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@lists.xen.org > http://lists.xen.org/xen-devel > =