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
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