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From: Greg Kurz <groug@kaod.org>
To: qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <fam@euphon.net>,
	qemu-block@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>,
	Greg Kurz <groug@kaod.org>, Max Reitz <mreitz@redhat.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	David Gibson <david@gibson.dropbear.id.au>
Subject: [for-6.1 4/4] virtio-scsi: Configure all host notifiers in a single MR transaction
Date: Wed,  7 Apr 2021 16:35:01 +0200
Message-ID: <20210407143501.244343-5-groug@kaod.org> (raw)
In-Reply-To: <20210407143501.244343-1-groug@kaod.org>

This allows the virtio-scsi-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 6m5.563s down to 1m2.884s 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 <groug@kaod.org>
---
 hw/scsi/virtio-scsi-dataplane.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
index b2cb3d9dcc64..28e003250a11 100644
--- a/hw/scsi/virtio-scsi-dataplane.c
+++ b/hw/scsi/virtio-scsi-dataplane.c
@@ -152,6 +152,8 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev)
         goto fail_guest_notifiers;
     }
 
+    memory_region_transaction_begin();
+
     rc = virtio_scsi_set_host_notifier(s, vs->ctrl_vq, 0);
     if (rc != 0) {
         goto fail_host_notifiers;
@@ -173,6 +175,8 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev)
         vq_init_count++;
     }
 
+    memory_region_transaction_commit();
+
     aio_context_acquire(s->ctx);
     virtio_queue_aio_set_host_notifier_handler(vs->ctrl_vq, s->ctx,
                                             virtio_scsi_data_plane_handle_ctrl);
@@ -192,6 +196,11 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev)
 fail_host_notifiers:
     for (i = 0; i < vq_init_count; i++) {
         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
+    }
+
+    memory_region_transaction_commit();
+
+    for (i = 0; i < vq_init_count; i++) {
         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
     }
     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
@@ -229,8 +238,15 @@ void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
 
     blk_drain_all(); /* ensure there are no in-flight requests */
 
+    memory_region_transaction_begin();
+
     for (i = 0; i < vs->conf.num_queues + 2; i++) {
         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
+    }
+
+    memory_region_transaction_commit();
+
+    for (i = 0; i < vs->conf.num_queues + 2; i++) {
         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
     }
 
-- 
2.26.3



  parent reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-07 14:34 [for-6.1 0/4] virtio: Improve boot time of virtio-scsi-pci and virtio-blk-pci Greg Kurz
2021-04-07 14:34 ` [for-6.1 1/4] virtio-blk: Fix rollback path in virtio_blk_data_plane_start() Greg Kurz
2021-04-07 14:34 ` [for-6.1 2/4] virtio-blk: Configure all host notifiers in a single MR transaction Greg Kurz
2021-05-05 10:14   ` Stefan Hajnoczi
2021-05-05 11:15     ` Greg Kurz
2021-05-06  8:15       ` Michael S. Tsirkin
2021-04-07 14:35 ` [for-6.1 3/4] virtio-scsi: Set host notifiers and callbacks separately Greg Kurz
2021-05-05 10:16   ` Stefan Hajnoczi
2021-04-07 14:35 ` Greg Kurz [this message]
2021-05-05 10:17   ` [for-6.1 4/4] virtio-scsi: Configure all host notifiers in a single MR transaction Stefan Hajnoczi
2021-04-19 15:31 ` [for-6.1 0/4] virtio: Improve boot time of virtio-scsi-pci and virtio-blk-pci Greg Kurz
2021-04-19 21:51 ` Michael S. Tsirkin

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