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| author | Stefan Hajnoczi <stefanha@redhat.com> | 2023-09-13 16:00:44 -0400 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2023-10-31 15:42:14 +0100 |
| commit | 84d61e5f36a73ed24742b7c7cf7b811e456dd024 (patch) | |
| tree | 420c313770c60a0f9aaa2487b296c6883535b4b0 /hw/virtio/trace-events | |
| parent | 433fcea40c31ff355f84da22a46977c2a1b596c3 (diff) | |
| download | focaccia-qemu-84d61e5f36a73ed24742b7c7cf7b811e456dd024.tar.gz focaccia-qemu-84d61e5f36a73ed24742b7c7cf7b811e456dd024.zip | |
virtio: use defer_call() in virtio_irqfd_notify()
virtio-blk and virtio-scsi invoke virtio_irqfd_notify() to send Used Buffer Notifications from an IOThread. This involves an eventfd write(2) syscall. Calling this repeatedly when completing multiple I/O requests in a row is wasteful. Use the defer_call() API to batch together virtio_irqfd_notify() calls made during thread pool (aio=threads), Linux AIO (aio=native), and io_uring (aio=io_uring) completion processing. Behavior is unchanged for emulated devices that do not use defer_call_begin()/defer_call_end() since defer_call() immediately invokes the callback when called outside a defer_call_begin()/defer_call_end() region. fio rw=randread bs=4k iodepth=64 numjobs=8 IOPS increases by ~9% with a single IOThread and 8 vCPUs. iodepth=1 decreases by ~1% but this could be noise. Detailed performance data and configuration specifics are available here: https://gitlab.com/stefanha/virt-playbooks/-/tree/blk_io_plug-irqfd This duplicates the BH that virtio-blk uses for batching. The next commit will remove it. Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-ID: <20230913200045.1024233-4-stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'hw/virtio/trace-events')
| -rw-r--r-- | hw/virtio/trace-events | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events index 1cb9027d1e..0af7a2886c 100644 --- a/hw/virtio/trace-events +++ b/hw/virtio/trace-events @@ -73,6 +73,7 @@ virtqueue_fill(void *vq, const void *elem, unsigned int len, unsigned int idx) " virtqueue_flush(void *vq, unsigned int count) "vq %p count %u" virtqueue_pop(void *vq, void *elem, unsigned int in_num, unsigned int out_num) "vq %p elem %p in_num %u out_num %u" virtio_queue_notify(void *vdev, int n, void *vq) "vdev %p n %d vq %p" +virtio_notify_irqfd_deferred_fn(void *vdev, void *vq) "vdev %p vq %p" virtio_notify_irqfd(void *vdev, void *vq) "vdev %p vq %p" virtio_notify(void *vdev, void *vq) "vdev %p vq %p" virtio_set_status(void *vdev, uint8_t val) "vdev %p val %u" |