Hi Greg, Thanks for your reply.
> > I'm Cc'ing qemu-devel like in your previous posts, so QEMU experts may > jump in. > > > What I understand from the requirement for our project is if we use > > virtio-blk it caches the pages in the guest. We would like to avoid that > > AFAIK this is true when you pass cache=none to -drive on the QEMU command > line. But there are other options such as writeback or writethrough, which > rely on the host page cache. > > Yes, we did explore these options already. > > and also we want to share those pages across multiple guests and when > they > > need some data they should get it from the host instead of using the > cached > > data at each guest. > > > > So you want all the guests to attach to the same block device or backing > file in > the host, correct ? AFAIK we cannot do that with virtio-blk indeed... and > virtio-9p > is only about sharing files, not block devices. > > Yes, we want to share the files. > Maybe you could share a big file between the host and all guests with 9p, > and > each guest can use the loop device to access the file as a block device... > but > even then, you'd have to deal with concurrent accesses... > > > Basically we are trying to cut down the memory foot print of the guests. > > > > If you're using KVM and your guests run the same distro or application, > you may try to use KSM (Kernel Same-page Merging) in the host. > > We are using these things also, we want to reduce the foot print as much as possible. Regards, Pradeep > > Regards, > > Pradeep > > > > On 31 March 2016 at 18:12, Greg Kurz <gk...@linux.vnet.ibm.com> wrote: > > > > > On Wed, 30 Mar 2016 16:27:48 +0200 > > > Pradeep Kiruvale <pradeepkiruv...@gmail.com> wrote: > > > > > > > Hi Greg, > > > > > > > > > > Hi Pradeep, > > > > > > > Thanks for the reply. > > > > > > > > Let me put it this way, virtio-blk-pci is used for block IO on the > > > devices > > > > shared between the guest and the host. > > > > > > I don't really understand the "devices shared between the guest and the > > > host" wording... virtio-blk-pci exposes a virtio-blk device through PCI > > > to the guest. The virtio-blk device can be backed by a file or a block > > > device from the host. > > > > > > > Here I want to share the file and have QoS between the guests. So I > am > > > > using the Virtio-9p-pci. > > > > > > > > > > What file ? > > > > > > > Basically I want to have QoS for virtio-9p-pci. > > > > > > > > > > Can you provide a more detailed scenario on the result you want to > reach ? > > > > > > > Regards, > > > > Pradeep > > > > > > > > > > Cheers. > > > > > > -- > > > Greg > > > > > > > On 30 March 2016 at 16:13, Greg Kurz <gk...@linux.vnet.ibm.com> > wrote: > > > > > > > > > On Wed, 30 Mar 2016 14:10:38 +0200 > > > > > Pradeep Kiruvale <pradeepkiruv...@gmail.com> wrote: > > > > > > > > > > > Hi All, > > > > > > > > > > > > Is virtio-9p-pci device only supports the fsdev deices? I am > trying > > > to > > > > > use > > > > > > -drive option for applying QoS for block device using > Virtio-9p-pci > > > > > device, > > > > > > but failing to create/add a device other than fsdev. Can you > please > > > help > > > > > me > > > > > > on this? > > > > > > > > > > > > Regards, > > > > > > Pradeep > > > > > > > > > > Hi Pradeep, > > > > > > > > > > Not sure to catch what you want to do but I confirm that > virti-9p-pci > > > only > > > > > supports > > > > > fsdev... if you want a block device, why don't you use > virtio-blk-pci ? > > > > > > > > > > Cheers. > > > > > > > > > > -- > > > > > Greg > > > > > > > > > > > > > > > > > >
