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virtio-blk: add x-data-plane=on|off performance feature

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The virtio-blk-data-plane feature is easy to integrate into
hw/virtio-blk.c.  The data plane can be started and stopped similar to
vhost-net.

Users can take advantage of the virtio-blk-data-plane feature using the
new -device virtio-blk-pci,x-data-plane=on property.

The x-data-plane name was chosen because at this stage the feature is
experimental and likely to see changes in the future.

If the VM configuration does not support virtio-blk-data-plane an error
message is printed.  Although we could fall back to regular virtio-blk,
I prefer the explicit approach since it prompts the user to fix their
configuration if they want the performance benefit of
virtio-blk-data-plane.

Limitations:
 * Only format=raw is supported
 * Live migration is not supported
 * Block jobs, hot unplug, and other operations fail with -EBUSY
 * I/O throttling limits are ignored
 * Only Linux hosts are supported due to Linux AIO usage

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2012-11-14 15:45:38 +01:00
parent e72f66a0a2
commit 392808b49b
2 changed files with 46 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
hw/virtio-blk.c
View File

@ -17,6 +17,9 @@
#include "hw/block-common.h"
#include "sysemu/blockdev.h"
#include "virtio-blk.h"
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
#include "hw/dataplane/virtio-blk.h"
#endif
#include "scsi-defs.h"
#ifdef __linux__
# include <scsi/sg.h>
@ -33,6 +36,9 @@ typedef struct VirtIOBlock
VirtIOBlkConf *blk;
unsigned short sector_mask;
DeviceState *qdev;
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
VirtIOBlockDataPlane *dataplane;
#endif
} VirtIOBlock;
static VirtIOBlock *to_virtio_blk(VirtIODevice *vdev)
@ -407,6 +413,16 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
.num_writes = 0,
};
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
/* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
* dataplane here instead of waiting for .set_status().
*/
if (s->dataplane) {
virtio_blk_data_plane_start(s->dataplane);
return;
}
#endif
while ((req = virtio_blk_get_request(s))) {
virtio_blk_handle_request(req, &mrb);
}
@ -446,8 +462,9 @@ static void virtio_blk_dma_restart_cb(void *opaque, int running,
{
VirtIOBlock *s = opaque;
if (!running)
if (!running) {
return;
}
if (!s->bh) {
s->bh = qemu_bh_new(virtio_blk_dma_restart_bh, s);
@ -457,6 +474,14 @@ static void virtio_blk_dma_restart_cb(void *opaque, int running,
static void virtio_blk_reset(VirtIODevice *vdev)
{
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
VirtIOBlock *s = to_virtio_blk(vdev);
if (s->dataplane) {
virtio_blk_data_plane_stop(s->dataplane);
}
#endif
/*
* This should cancel pending requests, but can't do nicely until there
* are per-device request lists.
@ -541,6 +566,12 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
VirtIOBlock *s = to_virtio_blk(vdev);
uint32_t features;
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
if (s->dataplane && !(status & VIRTIO_CONFIG_S_DRIVER)) {
virtio_blk_data_plane_stop(s->dataplane);
}
#endif
if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
return;
}
@ -638,6 +669,12 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
if (!virtio_blk_data_plane_create(&s->vdev, blk, &s->dataplane)) {
virtio_cleanup(&s->vdev);
return NULL;
}
#endif
qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
s->qdev = dev;
@ -655,6 +692,11 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
void virtio_blk_exit(VirtIODevice *vdev)
{
VirtIOBlock *s = to_virtio_blk(vdev);
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
virtio_blk_data_plane_destroy(s->dataplane);
s->dataplane = NULL;
#endif
unregister_savevm(s->qdev, "virtio-blk", s);
blockdev_mark_auto_del(s->bs);
virtio_cleanup(vdev);

3
hw/virtio-pci.c
View File

@ -896,6 +896,9 @@ static Property virtio_blk_properties[] = {
#endif
DEFINE_PROP_BIT("config-wce", VirtIOPCIProxy, blk.config_wce, 0, true),
DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
DEFINE_PROP_BIT("x-data-plane", VirtIOPCIProxy, blk.data_plane, 0, false),
#endif
DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
DEFINE_PROP_END_OF_LIST(),