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Re: [Qemu-devel] [RFC v9 18/27] virtio-blk: Call ioctl() directly instea
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From: |
Stefan Hajnoczi |
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Subject: |
Re: [Qemu-devel] [RFC v9 18/27] virtio-blk: Call ioctl() directly instead of irqfd |
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Date: |
Thu, 19 Jul 2012 10:11:49 +0100 |
On Wed, Jul 18, 2012 at 4:40 PM, Michael S. Tsirkin <address@hidden> wrote:
> On Wed, Jul 18, 2012 at 04:07:45PM +0100, Stefan Hajnoczi wrote:
>> Optimize for the MSI-X enabled and vector unmasked case where it is
>> possible to issue the KVM ioctl() directly instead of using irqfd.
>
> Why? Is an ioctl faster?
I have no benchmark results comparing irqfd against direct ioctl. It
would be interesting to know if this "optimization" is worthwhile and
how much of a win it is.
The reasoning is that the irqfd code path signals an eventfd and then
kvm.ko's poll handler injects the interrupt. The ioctl calls straight
into kvm.ko and skips the signalling/poll step.
Stefan
- [Qemu-devel] [RFC v9 12/27] virtio-blk: Add workaround for BUG_ON() dependency in virtio_ring.h, (continued)
- [Qemu-devel] [RFC v9 12/27] virtio-blk: Add workaround for BUG_ON() dependency in virtio_ring.h, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 11/27] virtio-blk: Indirect vring and flush support, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 14/27] virtio-blk: Use pthreads instead of qemu-thread, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 16/27] virtio-blk: Kick data plane thread using event notifier set, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 08/27] virtio-blk: Read requests from the vring, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 18/27] virtio-blk: Call ioctl() directly instead of irqfd, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 21/27] virtio-blk: Add basic request merging, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 20/27] virtio-blk: Add ioscheduler to detect mergable requests, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 26/27] msix: use upstream kvm_irqchip_set_irq(), Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 19/27] virtio-blk: Disable guest->host notifies while processing vring, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 27/27] virtio-blk: add EVENT_IDX support to dataplane, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 24/27] virtio-blk: fix incorrect length, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 17/27] virtio-blk: Use guest notifier to raise interrupts, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 25/27] msix: fix irqchip breakage in msix_try_notify_from_thread(), Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 22/27] virtio-blk: Fix request merging, Stefan Hajnoczi, 2012/07/18