On Thu, Jul 09, 2015 at 04:29:30PM +0300, Michael S. Tsirkin wrote: > On Thu, Jul 09, 2015 at 02:22:48PM +0100, Stefan Hajnoczi wrote: > > On Wed, Jul 08, 2015 at 05:37:12PM +0300, Michael S. Tsirkin wrote: > > > On Thu, Jul 02, 2015 at 09:21:21AM +0800, Fam Zheng wrote: > > > > On Wed, 07/01 22:45, Naredula Janardhana Reddy wrote: > > > > > HI, > > > > > I am trying to improve the throughput of virtio-blk for my > > > > > kernel ( > > > > > https://github.com/naredula-jana/Jiny-Kernel ) to make use of the > > > > > multi-core using multi-queue. But I found the latest qemu does not > > > > > support > > > > > multiqueue for virtio-blk, The feature flag does not return > > > > > multi-queue > > > > > support. Do we have any patches to the qemu for enabling multi-queue > > > > > for > > > > > virtio-blk similar to that of virtio-net. Can someone help some > > > > > pointers > > > > > related to this.. > > > > > > > > There was a series last year adding support for multi-queue but wan't > > > > merged to > > > > the code base: > > > > > > > > http://comments.gmane.org/gmane.comp.emulators.qemu/289126 > > > > > > > > Fam > > > > > > Looks like it was mostly about the missing GPL license on some files. > > > Or did I miss some bigger issues? > > > > I reviewed the series again. The most important part: > > > > It was not a true multiqueue implementation - all the virtqueues are > > handled from a single thread in QEMU. The reason for this is that > > QEMU's block layer isn't threadsafe so a lot of work is necessary to > > support true multiqueue. > > > > Also, the performance numbers quoted cannot be attributed to multiqueue > > due to the number of additional changes the series made. In the > > meantime, some of these additional changes have been merged as separate > > series. > > > > On the positive side, we do need something similar to the last 3 patches > > to expose multiqueue to the guest. But it will require much more work > > in QEMU to achieve true multiqueue. > > > > Stefan > > Might this be useful as an intermediate step, e.g. for testing > guest code?
Yes. It will have a performance impact since there are now more virtqueues and interrupts. It just won't scale the same way blk-mq does on the host. I'll put together patches based on qemu.git/master. Stefan
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