qemu/qapi/block-export.json
Stefan Hajnoczi d9b495f9c6 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>
2020-10-23 13:42:16 +01:00

324 lines
9.1 KiB
Python

# -*- Mode: Python -*-
# vim: filetype=python
##
# == Block device exports
##
{ 'include': 'sockets.json' }
##
# @NbdServerOptions:
#
# Keep this type consistent with the nbd-server-start arguments. The only
# intended difference is using SocketAddress instead of SocketAddressLegacy.
#
# @addr: Address on which to listen.
# @tls-creds: ID of the TLS credentials object (since 2.6).
# @tls-authz: ID of the QAuthZ authorization object used to validate
# the client's x509 distinguished name. This object is
# is only resolved at time of use, so can be deleted and
# recreated on the fly while the NBD server is active.
# If missing, it will default to denying access (since 4.0).
# @max-connections: The maximum number of connections to allow at the same
# time, 0 for unlimited. (since 5.2; default: 0)
#
# Since: 4.2
##
{ 'struct': 'NbdServerOptions',
'data': { 'addr': 'SocketAddress',
'*tls-creds': 'str',
'*tls-authz': 'str',
'*max-connections': 'uint32' } }
##
# @nbd-server-start:
#
# Start an NBD server listening on the given host and port. Block
# devices can then be exported using @nbd-server-add. The NBD
# server will present them as named exports; for example, another
# QEMU instance could refer to them as "nbd:HOST:PORT:exportname=NAME".
#
# Keep this type consistent with the NbdServerOptions type. The only intended
# difference is using SocketAddressLegacy instead of SocketAddress.
#
# @addr: Address on which to listen.
# @tls-creds: ID of the TLS credentials object (since 2.6).
# @tls-authz: ID of the QAuthZ authorization object used to validate
# the client's x509 distinguished name. This object is
# is only resolved at time of use, so can be deleted and
# recreated on the fly while the NBD server is active.
# If missing, it will default to denying access (since 4.0).
# @max-connections: The maximum number of connections to allow at the same
# time, 0 for unlimited. (since 5.2; default: 0)
#
# Returns: error if the server is already running.
#
# Since: 1.3.0
##
{ 'command': 'nbd-server-start',
'data': { 'addr': 'SocketAddressLegacy',
'*tls-creds': 'str',
'*tls-authz': 'str',
'*max-connections': 'uint32' } }
##
# @BlockExportOptionsNbd:
#
# An NBD block export (options shared between nbd-server-add and the NBD branch
# of block-export-add).
#
# @name: Export name. If unspecified, the @device parameter is used as the
# export name. (Since 2.12)
#
# @description: Free-form description of the export, up to 4096 bytes.
# (Since 5.0)
#
# @bitmap: Also export the dirty bitmap reachable from @device, so the
# NBD client can use NBD_OPT_SET_META_CONTEXT with
# "qemu:dirty-bitmap:NAME" to inspect the bitmap. (since 4.0)
#
# Since: 5.0
##
{ 'struct': 'BlockExportOptionsNbd',
'data': { '*name': 'str', '*description': 'str',
'*bitmap': 'str' } }
##
# @BlockExportOptionsVhostUserBlk:
#
# A vhost-user-blk block export.
#
# @addr: The vhost-user socket on which to listen. Both 'unix' and 'fd'
# 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',
'*num-queues': 'uint16'} }
##
# @NbdServerAddOptions:
#
# An NBD block export.
#
# @device: The device name or node name of the node to be exported
#
# @writable: Whether clients should be able to write to the device via the
# NBD connection (default false).
#
# Since: 5.0
##
{ 'struct': 'NbdServerAddOptions',
'base': 'BlockExportOptionsNbd',
'data': { 'device': 'str',
'*writable': 'bool' } }
##
# @nbd-server-add:
#
# Export a block node to QEMU's embedded NBD server.
#
# The export name will be used as the id for the resulting block export.
#
# Features:
# @deprecated: This command is deprecated. Use @block-export-add instead.
#
# Returns: error if the server is not running, or export with the same name
# already exists.
#
# Since: 1.3.0
##
{ 'command': 'nbd-server-add',
'data': 'NbdServerAddOptions', 'boxed': true, 'features': ['deprecated'] }
##
# @BlockExportRemoveMode:
#
# Mode for removing a block export.
#
# @safe: Remove export if there are no existing connections, fail otherwise.
#
# @hard: Drop all connections immediately and remove export.
#
# Potential additional modes to be added in the future:
#
# hide: Just hide export from new clients, leave existing connections as is.
# Remove export after all clients are disconnected.
#
# soft: Hide export from new clients, answer with ESHUTDOWN for all further
# requests from existing clients.
#
# Since: 2.12
##
{'enum': 'BlockExportRemoveMode', 'data': ['safe', 'hard']}
##
# @nbd-server-remove:
#
# Remove NBD export by name.
#
# @name: Block export id.
#
# @mode: Mode of command operation. See @BlockExportRemoveMode description.
# Default is 'safe'.
#
# Features:
# @deprecated: This command is deprecated. Use @block-export-del instead.
#
# Returns: error if
# - the server is not running
# - export is not found
# - mode is 'safe' and there are existing connections
#
# Since: 2.12
##
{ 'command': 'nbd-server-remove',
'data': {'name': 'str', '*mode': 'BlockExportRemoveMode'},
'features': ['deprecated'] }
##
# @nbd-server-stop:
#
# Stop QEMU's embedded NBD server, and unregister all devices previously
# added via @nbd-server-add.
#
# Since: 1.3.0
##
{ 'command': 'nbd-server-stop' }
##
# @BlockExportType:
#
# An enumeration of block export types
#
# @nbd: NBD export
# @vhost-user-blk: vhost-user-blk export (since 5.2)
#
# Since: 4.2
##
{ 'enum': 'BlockExportType',
'data': [ 'nbd', 'vhost-user-blk' ] }
##
# @BlockExportOptions:
#
# Describes a block export, i.e. how single node should be exported on an
# external interface.
#
# @id: A unique identifier for the block export (across all export types)
#
# @node-name: The node name of the block node to be exported (since: 5.2)
#
# @writable: True if clients should be able to write to the export
# (default false)
#
# @writethrough: If true, caches are flushed after every write request to the
# export before completion is signalled. (since: 5.2;
# default: false)
#
# @iothread: The name of the iothread object where the export will run. The
# default is to use the thread currently associated with the
# block node. (since: 5.2)
#
# @fixed-iothread: True prevents the block node from being moved to another
# thread while the export is active. If true and @iothread is
# given, export creation fails if the block node cannot be
# moved to the iothread. The default is false. (since: 5.2)
#
# Since: 4.2
##
{ 'union': 'BlockExportOptions',
'base': { 'type': 'BlockExportType',
'id': 'str',
'*fixed-iothread': 'bool',
'*iothread': 'str',
'node-name': 'str',
'*writable': 'bool',
'*writethrough': 'bool' },
'discriminator': 'type',
'data': {
'nbd': 'BlockExportOptionsNbd',
'vhost-user-blk': 'BlockExportOptionsVhostUserBlk'
} }
##
# @block-export-add:
#
# Creates a new block export.
#
# Since: 5.2
##
{ 'command': 'block-export-add',
'data': 'BlockExportOptions', 'boxed': true }
##
# @block-export-del:
#
# Request to remove a block export. This drops the user's reference to the
# export, but the export may still stay around after this command returns until
# the shutdown of the export has completed.
#
# @id: Block export id.
#
# @mode: Mode of command operation. See @BlockExportRemoveMode description.
# Default is 'safe'.
#
# Returns: Error if the export is not found or @mode is 'safe' and the export
# is still in use (e.g. by existing client connections)
#
# Since: 5.2
##
{ 'command': 'block-export-del',
'data': { 'id': 'str', '*mode': 'BlockExportRemoveMode' } }
##
# @BLOCK_EXPORT_DELETED:
#
# Emitted when a block export is removed and its id can be reused.
#
# @id: Block export id.
#
# Since: 5.2
##
{ 'event': 'BLOCK_EXPORT_DELETED',
'data': { 'id': 'str' } }
##
# @BlockExportInfo:
#
# Information about a single block export.
#
# @id: The unique identifier for the block export
#
# @type: The block export type
#
# @node-name: The node name of the block node that is exported
#
# @shutting-down: True if the export is shutting down (e.g. after a
# block-export-del command, but before the shutdown has
# completed)
#
# Since: 5.2
##
{ 'struct': 'BlockExportInfo',
'data': { 'id': 'str',
'type': 'BlockExportType',
'node-name': 'str',
'shutting-down': 'bool' } }
##
# @query-block-exports:
#
# Returns: A list of BlockExportInfo describing all block exports
#
# Since: 5.2
##
{ 'command': 'query-block-exports', 'returns': ['BlockExportInfo'] }