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[Qemu-devel] [PULL 06/50] virtio-scsi: Add virtqueue_size parameter allo
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 06/50] virtio-scsi: Add virtqueue_size parameter allowing virtqueue size to be set. |
Date: |
Tue, 19 Sep 2017 14:28:55 +0200 |
From: "Richard W.M. Jones" <address@hidden>
Since Linux switched to blk-mq as the default in Linux commit
5c279bd9e406 ("scsi: default to scsi-mq"), virtio-scsi LUNs consume
about 10x as much guest kernel memory.
This commit allows you to choose the virtqueue size for each
virtio-scsi-pci controller like this:
-device virtio-scsi-pci,id=scsi,virtqueue_size=16
The default is still 128 as before. Using smaller virtqueue_size
allows many more disks to be added to small memory virtual machines.
For a 1 vCPU, 500 MB, no swap VM I observed:
With scsi-mq enabled (upstream kernel): 175 disks
-"- ditto -"- virtqueue_size=64: 318 disks
-"- ditto -"- virtqueue_size=16: 775 disks
With scsi-mq disabled (kernel before 5c279bd9e406): 1755 disks
Note that to have any effect, this requires a kernel patch:
https://lkml.org/lkml/2017/8/10/689
Signed-off-by: Richard W.M. Jones <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
hw/scsi/virtio-scsi.c | 8 +++++---
include/hw/virtio/virtio-scsi.h | 2 +-
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index eb63944..aca1909 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -867,10 +867,10 @@ void virtio_scsi_common_realize(DeviceState *dev,
s->sense_size = VIRTIO_SCSI_SENSE_DEFAULT_SIZE;
s->cdb_size = VIRTIO_SCSI_CDB_DEFAULT_SIZE;
- s->ctrl_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, ctrl);
- s->event_vq = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, evt);
+ s->ctrl_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, ctrl);
+ s->event_vq = virtio_add_queue(vdev, s->conf.virtqueue_size, evt);
for (i = 0; i < s->conf.num_queues; i++) {
- s->cmd_vqs[i] = virtio_add_queue(vdev, VIRTIO_SCSI_VQ_SIZE, cmd);
+ s->cmd_vqs[i] = virtio_add_queue(vdev, s->conf.virtqueue_size, cmd);
}
}
@@ -917,6 +917,8 @@ static void virtio_scsi_device_unrealize(DeviceState *dev,
Error **errp)
static Property virtio_scsi_properties[] = {
DEFINE_PROP_UINT32("num_queues", VirtIOSCSI, parent_obj.conf.num_queues,
1),
+ DEFINE_PROP_UINT32("virtqueue_size", VirtIOSCSI,
+ parent_obj.conf.virtqueue_size, 128),
DEFINE_PROP_UINT32("max_sectors", VirtIOSCSI, parent_obj.conf.max_sectors,
0xFFFF),
DEFINE_PROP_UINT32("cmd_per_lun", VirtIOSCSI, parent_obj.conf.cmd_per_lun,
diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
index de6ae5a..4c0bcdb 100644
--- a/include/hw/virtio/virtio-scsi.h
+++ b/include/hw/virtio/virtio-scsi.h
@@ -32,7 +32,6 @@
#define VIRTIO_SCSI(obj) \
OBJECT_CHECK(VirtIOSCSI, (obj), TYPE_VIRTIO_SCSI)
-#define VIRTIO_SCSI_VQ_SIZE 128
#define VIRTIO_SCSI_MAX_CHANNEL 0
#define VIRTIO_SCSI_MAX_TARGET 255
#define VIRTIO_SCSI_MAX_LUN 16383
@@ -48,6 +47,7 @@ typedef struct virtio_scsi_config VirtIOSCSIConfig;
struct VirtIOSCSIConf {
uint32_t num_queues;
+ uint32_t virtqueue_size;
uint32_t max_sectors;
uint32_t cmd_per_lun;
#ifdef CONFIG_VHOST_SCSI
--
1.8.3.1
- [Qemu-devel] [PULL 00/50] Misc patches for 2017-09-19, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 02/50] target/i386: set rip_offset for further SSE instructions, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 05/50] target/i386: fix phminposuw in-place operation, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 04/50] target/i386: fix pcmpxstrx substring search, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 03/50] target/i386: fix packusdw in-place operation, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 01/50] target/i386: fix pmovsx/pmovzx in-place operations, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 06/50] virtio-scsi: Add virtqueue_size parameter allowing virtqueue size to be set.,
Paolo Bonzini <=
- [Qemu-devel] [PULL 09/50] scsi: Improve scsi_sense_to_errno, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 08/50] scsi: Refactor scsi sense interpreting code, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 11/50] scsi-block: Support rerror/werror, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 14/50] scsi: introduce scsi_build_sense, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 10/50] scsi: Introduce scsi_sense_buf_to_errno, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 07/50] scsi-bus: correct responses for INQUIRY and REQUEST SENSE, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 12/50] scsi: rename scsi_build_sense to scsi_convert_sense, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 15/50] scsi: introduce sg_io_sense_from_errno, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 16/50] scsi: move block/scsi.h to include/scsi/constants.h, Paolo Bonzini, 2017/09/19
- [Qemu-devel] [PULL 20/50] i386/kvm: introduce tsc_is_stable_and_known(), Paolo Bonzini, 2017/09/19