qemu/include/hw/virtio/virtio-scsi.h
Richard W.M. Jones 5c0919d020 virtio-scsi: Add virtqueue_size parameter allowing virtqueue size to be set.
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 <rjones@redhat.com>
Message-Id: <20170810165255.20865-1-rjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2017-09-19 14:09:11 +02:00

162 lines
4.4 KiB
C

/*
* Virtio SCSI HBA
*
* Copyright IBM, Corp. 2010
*
* Authors:
* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#ifndef QEMU_VIRTIO_SCSI_H
#define QEMU_VIRTIO_SCSI_H
/* Override CDB/sense data size: they are dynamic (guest controlled) in QEMU */
#define VIRTIO_SCSI_CDB_SIZE 0
#define VIRTIO_SCSI_SENSE_SIZE 0
#include "standard-headers/linux/virtio_scsi.h"
#include "hw/virtio/virtio.h"
#include "hw/pci/pci.h"
#include "hw/scsi/scsi.h"
#include "chardev/char-fe.h"
#include "sysemu/iothread.h"
#define TYPE_VIRTIO_SCSI_COMMON "virtio-scsi-common"
#define VIRTIO_SCSI_COMMON(obj) \
OBJECT_CHECK(VirtIOSCSICommon, (obj), TYPE_VIRTIO_SCSI_COMMON)
#define TYPE_VIRTIO_SCSI "virtio-scsi-device"
#define VIRTIO_SCSI(obj) \
OBJECT_CHECK(VirtIOSCSI, (obj), TYPE_VIRTIO_SCSI)
#define VIRTIO_SCSI_MAX_CHANNEL 0
#define VIRTIO_SCSI_MAX_TARGET 255
#define VIRTIO_SCSI_MAX_LUN 16383
typedef struct virtio_scsi_cmd_req VirtIOSCSICmdReq;
typedef struct virtio_scsi_cmd_resp VirtIOSCSICmdResp;
typedef struct virtio_scsi_ctrl_tmf_req VirtIOSCSICtrlTMFReq;
typedef struct virtio_scsi_ctrl_tmf_resp VirtIOSCSICtrlTMFResp;
typedef struct virtio_scsi_ctrl_an_req VirtIOSCSICtrlANReq;
typedef struct virtio_scsi_ctrl_an_resp VirtIOSCSICtrlANResp;
typedef struct virtio_scsi_event VirtIOSCSIEvent;
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
char *vhostfd;
char *wwpn;
#endif
CharBackend chardev;
uint32_t boot_tpgt;
IOThread *iothread;
};
struct VirtIOSCSI;
typedef struct VirtIOSCSICommon {
VirtIODevice parent_obj;
VirtIOSCSIConf conf;
uint32_t sense_size;
uint32_t cdb_size;
VirtQueue *ctrl_vq;
VirtQueue *event_vq;
VirtQueue **cmd_vqs;
} VirtIOSCSICommon;
typedef struct VirtIOSCSI {
VirtIOSCSICommon parent_obj;
SCSIBus bus;
int resetting;
bool events_dropped;
/* Fields for dataplane below */
AioContext *ctx; /* one iothread per virtio-scsi-pci for now */
bool dataplane_started;
bool dataplane_starting;
bool dataplane_stopping;
bool dataplane_fenced;
uint32_t host_features;
} VirtIOSCSI;
typedef struct VirtIOSCSIReq {
/* Note:
* - fields up to resp_iov are initialized by virtio_scsi_init_req;
* - fields starting at vring are zeroed by virtio_scsi_init_req.
* */
VirtQueueElement elem;
VirtIOSCSI *dev;
VirtQueue *vq;
QEMUSGList qsgl;
QEMUIOVector resp_iov;
union {
/* Used for two-stage request submission */
QTAILQ_ENTRY(VirtIOSCSIReq) next;
/* Used for cancellation of request during TMFs */
int remaining;
};
SCSIRequest *sreq;
size_t resp_size;
enum SCSIXferMode mode;
union {
VirtIOSCSICmdResp cmd;
VirtIOSCSICtrlTMFResp tmf;
VirtIOSCSICtrlANResp an;
VirtIOSCSIEvent event;
} resp;
union {
VirtIOSCSICmdReq cmd;
VirtIOSCSICtrlTMFReq tmf;
VirtIOSCSICtrlANReq an;
} req;
} VirtIOSCSIReq;
static inline void virtio_scsi_acquire(VirtIOSCSI *s)
{
if (s->ctx) {
aio_context_acquire(s->ctx);
}
}
static inline void virtio_scsi_release(VirtIOSCSI *s)
{
if (s->ctx) {
aio_context_release(s->ctx);
}
}
void virtio_scsi_common_realize(DeviceState *dev,
VirtIOHandleOutput ctrl,
VirtIOHandleOutput evt,
VirtIOHandleOutput cmd,
Error **errp);
void virtio_scsi_common_unrealize(DeviceState *dev, Error **errp);
bool virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq);
bool virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq);
bool virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq);
void virtio_scsi_init_req(VirtIOSCSI *s, VirtQueue *vq, VirtIOSCSIReq *req);
void virtio_scsi_free_req(VirtIOSCSIReq *req);
void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
uint32_t event, uint32_t reason);
void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp);
int virtio_scsi_dataplane_start(VirtIODevice *s);
void virtio_scsi_dataplane_stop(VirtIODevice *s);
#endif /* QEMU_VIRTIO_SCSI_H */