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block/export: add vhost-user-blk multi-queue support 

Allow the number of queues to be configured using --export
vhost-user-blk,num-queues=N. This setting should match the QEMU --device
vhost-user-blk-pci,num-queues=N setting but QEMU vhost-user-blk.c lowers
its own value if the vhost-user-blk backend offers fewer queues than
QEMU.

The vhost-user-blk-server.c code is already capable of multi-queue. All
virtqueue processing runs in the same AioContext. No new locking is
needed.

Add the num-queues=N option and set the VIRTIO_BLK_F_MQ feature bit.
Note that the feature bit only announces the presence of the num_queues
configuration space field. It does not promise that there is more than 1
virtqueue, so we can set it unconditionally.

I tested multi-queue by running a random read fio test with numjobs=4 on
an -smp 4 guest. After the benchmark finished the guest /proc/interrupts
file showed activity on all 4 virtio-blk MSI-X. The /sys/block/vda/mq/
directory shows that Linux blk-mq has 4 queues configured.

An automated test is included in the next commit.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20201001144604.559733-2-stefanha@redhat.com
[Fixed accidental tab characters as suggested by Markus Armbruster
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-10-01 15:46:03 +01:00
parent f51d23c80a
commit d9b495f9c6
2 changed files with 25 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
block/export/vhost-user-blk-server.c
View File

@ -21,7 +21,7 @@
#include "util/block-helpers.h"
enum {
VHOST_USER_BLK_MAX_QUEUES = 1,
VHOST_USER_BLK_NUM_QUEUES_DEFAULT = 1,
};
struct virtio_blk_inhdr {
unsigned char status;
@ -242,6 +242,7 @@ static uint64_t vu_blk_get_features(VuDev *dev)
1ull << VIRTIO_BLK_F_DISCARD |
1ull << VIRTIO_BLK_F_WRITE_ZEROES |
1ull << VIRTIO_BLK_F_CONFIG_WCE |
1ull << VIRTIO_BLK_F_MQ |
1ull << VIRTIO_F_VERSION_1 |
1ull << VIRTIO_RING_F_INDIRECT_DESC |
1ull << VIRTIO_RING_F_EVENT_IDX |
@ -338,7 +339,9 @@ static void blk_aio_detach(void *opaque)
static void
vu_blk_initialize_config(BlockDriverState *bs,
struct virtio_blk_config *config, uint32_t blk_size)
struct virtio_blk_config *config,
uint32_t blk_size,
uint16_t num_queues)
{
config->capacity = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
config->blk_size = blk_size;
@ -346,7 +349,7 @@ vu_blk_initialize_config(BlockDriverState *bs,
config->seg_max = 128 - 2;
config->min_io_size = 1;
config->opt_io_size = 1;
config->num_queues = VHOST_USER_BLK_MAX_QUEUES;
config->num_queues = num_queues;
config->max_discard_sectors = 32768;
config->max_discard_seg = 1;
config->discard_sector_alignment = config->blk_size >> 9;
@ -368,6 +371,7 @@ static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
BlockExportOptionsVhostUserBlk *vu_opts = &opts->u.vhost_user_blk;
Error *local_err = NULL;
uint64_t logical_block_size;
uint16_t num_queues = VHOST_USER_BLK_NUM_QUEUES_DEFAULT;
vexp->writable = opts->writable;
vexp->blkcfg.wce = 0;
@ -385,15 +389,23 @@ static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
}
vexp->blk_size = logical_block_size;
blk_set_guest_block_size(exp->blk, logical_block_size);
if (vu_opts->has_num_queues) {
num_queues = vu_opts->num_queues;
}
if (num_queues == 0) {
error_setg(errp, "num-queues must be greater than 0");
return -EINVAL;
}
vu_blk_initialize_config(blk_bs(exp->blk), &vexp->blkcfg,
logical_block_size);
logical_block_size, num_queues);
blk_add_aio_context_notifier(exp->blk, blk_aio_attached, blk_aio_detach,
vexp);
if (!vhost_user_server_start(&vexp->vu_server, vu_opts->addr, exp->ctx,
VHOST_USER_BLK_MAX_QUEUES, &vu_blk_iface,
errp)) {
num_queues, &vu_blk_iface, errp)) {
blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
blk_aio_detach, vexp);
return -EADDRNOTAVAIL;

10
qapi/block-export.json
View File

@ -93,11 +93,15 @@
# SocketAddress types are supported. Passed fds must be UNIX domain
# sockets.
# @logical-block-size: Logical block size in bytes. Defaults to 512 bytes.
# @num-queues: Number of request virtqueues. Must be greater than 0. Defaults
# to 1.
#
# Since: 5.2
##
{ 'struct': 'BlockExportOptionsVhostUserBlk',
'data': { 'addr': 'SocketAddress', '*logical-block-size': 'size' } }
'data': { 'addr': 'SocketAddress',
'*logical-block-size': 'size',
'*num-queues': 'uint16'} }
##
# @NbdServerAddOptions:
@ -233,8 +237,8 @@
{ 'union': 'BlockExportOptions',
'base': { 'type': 'BlockExportType',
'id': 'str',
'*fixed-iothread': 'bool',
'*iothread': 'str',
'*fixed-iothread': 'bool',
'*iothread': 'str',
'node-name': 'str',
'*writable': 'bool',
'*writethrough': 'bool' },