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
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