From d0267da614890b8f817364ae25850cdbb580a569 Mon Sep 17 00:00:00 2001 From: Greg Kurz Date: Wed, 7 Apr 2021 16:34:59 +0200 Subject: [PATCH] virtio-blk: Configure all host notifiers in a single MR transaction This allows the virtio-blk-pci device to batch the setup of all its host notifiers. This significantly improves boot time of VMs with a high number of vCPUs, e.g. from 3m26.186s down to 0m58.023s for a pseries machine with 384 vCPUs. Note that memory_region_transaction_commit() must be called before virtio_bus_cleanup_host_notifier() because the latter might close ioeventfds that the transaction still assumes to be around when it commits. Signed-off-by: Greg Kurz Message-Id: <20210407143501.244343-3-groug@kaod.org> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/block/dataplane/virtio-blk.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index d7b5c95d26..cd81893d1d 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -198,19 +198,30 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev) goto fail_guest_notifiers; } + memory_region_transaction_begin(); + /* Set up virtqueue notify */ for (i = 0; i < nvqs; i++) { r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, true); if (r != 0) { + int j = i; + fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r); while (i--) { virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false); + } + + memory_region_transaction_commit(); + + while (j--) { virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i); } goto fail_host_notifiers; } } + memory_region_transaction_commit(); + s->starting = false; vblk->dataplane_started = true; trace_virtio_blk_data_plane_start(s); @@ -246,8 +257,15 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev) return 0; fail_aio_context: + memory_region_transaction_begin(); + for (i = 0; i < nvqs; i++) { virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false); + } + + memory_region_transaction_commit(); + + for (i = 0; i < nvqs; i++) { virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i); } fail_host_notifiers: @@ -312,8 +330,15 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev) aio_context_release(s->ctx); + memory_region_transaction_begin(); + for (i = 0; i < nvqs; i++) { virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false); + } + + memory_region_transaction_commit(); + + for (i = 0; i < nvqs; i++) { virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i); }