5c0919d020
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>
162 lines
4.4 KiB
C
162 lines
4.4 KiB
C
/*
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* Virtio SCSI HBA
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*
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* Copyright IBM, Corp. 2010
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef QEMU_VIRTIO_SCSI_H
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#define QEMU_VIRTIO_SCSI_H
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/* Override CDB/sense data size: they are dynamic (guest controlled) in QEMU */
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#define VIRTIO_SCSI_CDB_SIZE 0
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#define VIRTIO_SCSI_SENSE_SIZE 0
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#include "standard-headers/linux/virtio_scsi.h"
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#include "hw/virtio/virtio.h"
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#include "hw/pci/pci.h"
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#include "hw/scsi/scsi.h"
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#include "chardev/char-fe.h"
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#include "sysemu/iothread.h"
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#define TYPE_VIRTIO_SCSI_COMMON "virtio-scsi-common"
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#define VIRTIO_SCSI_COMMON(obj) \
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OBJECT_CHECK(VirtIOSCSICommon, (obj), TYPE_VIRTIO_SCSI_COMMON)
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#define TYPE_VIRTIO_SCSI "virtio-scsi-device"
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#define VIRTIO_SCSI(obj) \
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OBJECT_CHECK(VirtIOSCSI, (obj), TYPE_VIRTIO_SCSI)
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#define VIRTIO_SCSI_MAX_CHANNEL 0
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#define VIRTIO_SCSI_MAX_TARGET 255
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#define VIRTIO_SCSI_MAX_LUN 16383
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typedef struct virtio_scsi_cmd_req VirtIOSCSICmdReq;
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typedef struct virtio_scsi_cmd_resp VirtIOSCSICmdResp;
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typedef struct virtio_scsi_ctrl_tmf_req VirtIOSCSICtrlTMFReq;
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typedef struct virtio_scsi_ctrl_tmf_resp VirtIOSCSICtrlTMFResp;
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typedef struct virtio_scsi_ctrl_an_req VirtIOSCSICtrlANReq;
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typedef struct virtio_scsi_ctrl_an_resp VirtIOSCSICtrlANResp;
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typedef struct virtio_scsi_event VirtIOSCSIEvent;
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typedef struct virtio_scsi_config VirtIOSCSIConfig;
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struct VirtIOSCSIConf {
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uint32_t num_queues;
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uint32_t virtqueue_size;
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uint32_t max_sectors;
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uint32_t cmd_per_lun;
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#ifdef CONFIG_VHOST_SCSI
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char *vhostfd;
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char *wwpn;
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#endif
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CharBackend chardev;
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uint32_t boot_tpgt;
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IOThread *iothread;
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};
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struct VirtIOSCSI;
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typedef struct VirtIOSCSICommon {
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VirtIODevice parent_obj;
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VirtIOSCSIConf conf;
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uint32_t sense_size;
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uint32_t cdb_size;
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VirtQueue *ctrl_vq;
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VirtQueue *event_vq;
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VirtQueue **cmd_vqs;
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} VirtIOSCSICommon;
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typedef struct VirtIOSCSI {
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VirtIOSCSICommon parent_obj;
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SCSIBus bus;
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int resetting;
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bool events_dropped;
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/* Fields for dataplane below */
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AioContext *ctx; /* one iothread per virtio-scsi-pci for now */
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bool dataplane_started;
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bool dataplane_starting;
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bool dataplane_stopping;
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bool dataplane_fenced;
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uint32_t host_features;
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} VirtIOSCSI;
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typedef struct VirtIOSCSIReq {
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/* Note:
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* - fields up to resp_iov are initialized by virtio_scsi_init_req;
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* - fields starting at vring are zeroed by virtio_scsi_init_req.
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* */
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VirtQueueElement elem;
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VirtIOSCSI *dev;
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VirtQueue *vq;
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QEMUSGList qsgl;
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QEMUIOVector resp_iov;
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union {
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/* Used for two-stage request submission */
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QTAILQ_ENTRY(VirtIOSCSIReq) next;
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/* Used for cancellation of request during TMFs */
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int remaining;
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};
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SCSIRequest *sreq;
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size_t resp_size;
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enum SCSIXferMode mode;
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union {
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VirtIOSCSICmdResp cmd;
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VirtIOSCSICtrlTMFResp tmf;
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VirtIOSCSICtrlANResp an;
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VirtIOSCSIEvent event;
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} resp;
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union {
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VirtIOSCSICmdReq cmd;
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VirtIOSCSICtrlTMFReq tmf;
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VirtIOSCSICtrlANReq an;
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} req;
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} VirtIOSCSIReq;
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static inline void virtio_scsi_acquire(VirtIOSCSI *s)
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{
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if (s->ctx) {
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aio_context_acquire(s->ctx);
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}
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}
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static inline void virtio_scsi_release(VirtIOSCSI *s)
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{
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if (s->ctx) {
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aio_context_release(s->ctx);
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}
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}
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void virtio_scsi_common_realize(DeviceState *dev,
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VirtIOHandleOutput ctrl,
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VirtIOHandleOutput evt,
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VirtIOHandleOutput cmd,
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Error **errp);
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void virtio_scsi_common_unrealize(DeviceState *dev, Error **errp);
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bool virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq);
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bool virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq);
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bool virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq);
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void virtio_scsi_init_req(VirtIOSCSI *s, VirtQueue *vq, VirtIOSCSIReq *req);
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void virtio_scsi_free_req(VirtIOSCSIReq *req);
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void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
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uint32_t event, uint32_t reason);
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void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp);
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int virtio_scsi_dataplane_start(VirtIODevice *s);
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void virtio_scsi_dataplane_stop(VirtIODevice *s);
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#endif /* QEMU_VIRTIO_SCSI_H */
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