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virtio-scsi: add iothread-vq-mapping parameter

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Allow virtio-scsi virtqueues to be assigned to different IOThreads. This
makes it possible to take advantage of host multi-queue block layer
scalability by assigning virtqueues that have affinity with vCPUs to
different IOThreads that have affinity with host CPUs. The same feature
was introduced for virtio-blk in the past:
https://developers.redhat.com/articles/2024/09/05/scaling-virtio-blk-disk-io-iothread-virtqueue-mapping

Here are fio randread 4k iodepth=64 results from a 4 vCPU guest with an
Intel P4800X SSD:
iothreads IOPS
------------------------------
1         189576
2         312698
4         346744

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20250311132616.1049687-12-stefanha@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
[kwolf: Updated 051 output, virtio-scsi can now use any iothread]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2025-03-11 21:26:14 +08:00 • committed by Kevin Wolf
parent b50629c335
commit 2e8e18c2e4
4 changed files with 108 additions and 52 deletions
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5
include/hw/virtio/virtio-scsi.h
View file

@ -22,6 +22,7 @@
#include "hw/virtio/virtio.h"
#include "hw/scsi/scsi.h"
#include "chardev/char-fe.h"
#include "qapi/qapi-types-virtio.h"
#include "system/iothread.h"
#define TYPE_VIRTIO_SCSI_COMMON "virtio-scsi-common"
@ -60,6 +61,7 @@ struct VirtIOSCSIConf {
CharBackend chardev;
uint32_t boot_tpgt;
IOThread *iothread;
IOThreadVirtQueueMappingList *iothread_vq_mapping_list;
};
struct VirtIOSCSI;
@ -97,7 +99,7 @@ struct VirtIOSCSI {
QTAILQ_HEAD(, VirtIOSCSIReq) tmf_bh_list;
/* Fields for dataplane below */
AioContext *ctx; /* one iothread per virtio-scsi-pci for now */
AioContext **vq_aio_context; /* per-virtqueue AioContext pointer */
bool dataplane_started;
bool dataplane_starting;
@ -115,6 +117,7 @@ void virtio_scsi_common_realize(DeviceState *dev,
void virtio_scsi_common_unrealize(DeviceState *dev);
void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp);
void virtio_scsi_dataplane_cleanup(VirtIOSCSI *s);
int virtio_scsi_dataplane_start(VirtIODevice *s);
void virtio_scsi_dataplane_stop(VirtIODevice *s);