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[PATCH v2 0/2] virtio-blk: add iothread-vq-mapping parameter
From: |
Stefan Hajnoczi |
Subject: |
[PATCH v2 0/2] virtio-blk: add iothread-vq-mapping parameter |
Date: |
Mon, 18 Sep 2023 12:16:02 -0400 |
virtio-blk and virtio-scsi devices need a way to specify the mapping between
IOThreads and virtqueues. At the moment all virtqueues are assigned to a single
IOThread or the main loop. This single thread can be a CPU bottleneck, so it is
necessary to allow finer-grained assignment to spread the load. With this
series applied, "pidstat -t 1" shows that guests with -smp 2 or higher are able
to exploit multiple IOThreads.
This series introduces command-line syntax for the new iothread-vq-mapping
property is as follows:
--device
'{"driver":"virtio-blk-pci","iothread-vq-mapping":[{"iothread":"iothread0","vqs":[0,1,2]},...]},...'
IOThreads are specified by name and virtqueues are specified by 0-based
index.
It will be common to simply assign virtqueues round-robin across a set
of IOThreads. A convenient syntax that does not require specifying
individual virtqueue indices is available:
--device
'{"driver":"virtio-blk-pci","iothread-vq-mapping":[{"iothread":"iothread0"},{"iothread":"iothread1"},...]},...'
There is no way to reassign virtqueues at runtime and I expect that to be a
very rare requirement.
Note that JSON --device syntax is required for the iothread-vq-mapping
parameter because it's non-scalar.
Based-on: 20230912231037.826804-1-stefanha@redhat.com ("[PATCH v3 0/5]
block-backend: process I/O in the current AioContext")
Stefan Hajnoczi (2):
qdev: add IOThreadVirtQueueMappingList property type
virtio-blk: add iothread-vq-mapping parameter
qapi/virtio.json | 30 +++++
hw/block/dataplane/virtio-blk.h | 3 +
include/hw/qdev-properties-system.h | 4 +
include/hw/virtio/virtio-blk.h | 2 +
hw/block/dataplane/virtio-blk.c | 163 +++++++++++++++++++++-------
hw/block/virtio-blk.c | 92 ++++++++++++++--
hw/core/qdev-properties-system.c | 47 ++++++++
7 files changed, 287 insertions(+), 54 deletions(-)
--
2.41.0
- [PATCH v2 0/2] virtio-blk: add iothread-vq-mapping parameter,
Stefan Hajnoczi <=