On Wed, Jul 18, 2012 at 04:07:27PM +0100, Stefan Hajnoczi wrote: > This series implements a dedicated thread for virtio-blk processing using > Linux > AIO for raw image files only. It is based on qemu-kvm.git a0bc8c3 and > somewhat > old but I wanted to share it on the list since it has been mentioned on > mailing > lists and IRC recently. > > These patches can be used for benchmarking and discussion about how to improve > block performance. Paolo Bonzini has also worked in this area and might want > to share his patches. > > The basic approach is: > 1. Each virtio-blk device has a thread dedicated to handling ioeventfd > signalling when the guest kicks the virtqueue. > 2. Requests are processed without going through the QEMU block layer using > Linux AIO directly. > 3. Completion interrupts are injected via ioctl from the dedicated thread. > > The series also contains request merging as a bdrv_aio_multiwrite() > equivalent. > This was only to get a comparison against the QEMU block layer and I would > drop > it for other types of analysis. > > The effect of this series is that O_DIRECT Linux AIO on raw files can bypass > the QEMU global mutex and block layer. This means higher performance.
Do you have any numbers at all? > A cleaned up version of this approach could be added to QEMU as a raw O_DIRECT > Linux AIO fast path. Image file formats, protocols, and other block layer > features are not supported by virtio-blk-data-plane. > > Git repo: > http://repo.or.cz/w/qemu-kvm/stefanha.git/shortlog/refs/heads/virtio-blk-data-plane > > Stefan Hajnoczi (27): > virtio-blk: Remove virtqueue request handling code > virtio-blk: Set up host notifier for data plane > virtio-blk: Data plane thread event loop > virtio-blk: Map vring > virtio-blk: Do cheapest possible memory mapping > virtio-blk: Take PCI memory range into account > virtio-blk: Put dataplane code into its own directory > virtio-blk: Read requests from the vring > virtio-blk: Add Linux AIO queue > virtio-blk: Stop data plane thread cleanly > virtio-blk: Indirect vring and flush support > virtio-blk: Add workaround for BUG_ON() dependency in virtio_ring.h > virtio-blk: Increase max requests for indirect vring > virtio-blk: Use pthreads instead of qemu-thread > notifier: Add a function to set the notifier > virtio-blk: Kick data plane thread using event notifier set > virtio-blk: Use guest notifier to raise interrupts > virtio-blk: Call ioctl() directly instead of irqfd > virtio-blk: Disable guest->host notifies while processing vring > virtio-blk: Add ioscheduler to detect mergable requests > virtio-blk: Add basic request merging > virtio-blk: Fix request merging > virtio-blk: Stub out SCSI commands > virtio-blk: fix incorrect length > msix: fix irqchip breakage in msix_try_notify_from_thread() > msix: use upstream kvm_irqchip_set_irq() > virtio-blk: add EVENT_IDX support to dataplane > > event_notifier.c | 7 + > event_notifier.h | 1 + > hw/dataplane/event-poll.h | 116 +++++++ > hw/dataplane/ioq.h | 128 ++++++++ > hw/dataplane/iosched.h | 97 ++++++ > hw/dataplane/vring.h | 334 ++++++++++++++++++++ > hw/msix.c | 15 + > hw/msix.h | 1 + > hw/virtio-blk.c | 753 > +++++++++++++++++++++------------------------ > hw/virtio-pci.c | 8 + > hw/virtio.c | 9 + > hw/virtio.h | 3 + > 12 files changed, 1074 insertions(+), 398 deletions(-) > create mode 100644 hw/dataplane/event-poll.h > create mode 100644 hw/dataplane/ioq.h > create mode 100644 hw/dataplane/iosched.h > create mode 100644 hw/dataplane/vring.h > > -- > 1.7.10.4
