Similar nits to patch 1, but a good patch nevertheless!
Il 11/09/2014 12:16, Fam Zheng ha scritto:
> The VirtQueueElement is a very big structure (> 4k), since it will be
> initialzed by virtqueue_pop, we can save the expensive zeroing here.
>
> This saves a few nanoseconds per request in my test:
>
> [fio-test] rw bs iodepth jobs bw iops
> latency
> --------------------------------------------------------------------------------------------
> Before read 4k 1 1 110 28269
> 34
> After read 4k 1 1 131 33745
> 28
>
> virtio-blk read 4k 1 1 217 55673
> 16
>
> Signed-off-by: Fam Zheng <f...@redhat.com>
> ---
> hw/scsi/virtio-scsi.c | 17 ++++++++++-------
> include/hw/virtio/virtio-scsi.h | 1 +
> 2 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index 86aba88..0792529 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -24,12 +24,12 @@
> typedef struct VirtIOSCSIReq {
> VirtIOSCSI *dev;
> VirtQueue *vq;
> - VirtQueueElement elem;
> QEMUSGList qsgl;
> + QEMUIOVector resp_iov;
> + VirtQueueElement elem;
Needs a comment where the zeroed section begins.
> SCSIRequest *sreq;
> size_t resp_size;
> enum SCSIXferMode mode;
> - QEMUIOVector resp_iov;
> union {
> VirtIOSCSICmdResp cmd;
> VirtIOSCSICtrlTMFResp tmf;
> @@ -44,6 +44,7 @@ typedef struct VirtIOSCSIReq {
> VirtIOSCSICtrlTMFReq tmf;
> VirtIOSCSICtrlANReq an;
> } req;
> + uint8_t cdb[VIRTIO_SCSI_CDB_SIZE_MAX];
> } VirtIOSCSIReq;
>
> QEMU_BUILD_BUG_ON(offsetof(VirtIOSCSIReq, req.cdb) !=
> @@ -68,15 +69,16 @@ static inline SCSIDevice
> *virtio_scsi_device_find(VirtIOSCSI *s, uint8_t *lun)
> static VirtIOSCSIReq *virtio_scsi_init_req(VirtIOSCSI *s, VirtQueue *vq)
> {
> VirtIOSCSIReq *req;
> - VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
> -
> - req = g_malloc0(sizeof(*req) + vs->cdb_size);
> + const size_t zero_skip = offsetof(VirtIOSCSIReq, elem)
> + + sizeof(VirtQueueElement);
>
> + req = g_slice_new(VirtIOSCSIReq);
I would use g_slice_alloc here, and avoid zeroing the largeish cdb field.
> req->vq = vq;
> req->dev = s;
> req->sreq = NULL;
This NULL initialization can be removed.
Paolo
> qemu_sglist_init(&req->qsgl, DEVICE(s), 8, &address_space_memory);
> qemu_iovec_init(&req->resp_iov, 1);
> + memset((uint8_t *)req + zero_skip, 0, sizeof(*req) - zero_skip);
> return req;
> }
>
> @@ -84,7 +86,7 @@ static void virtio_scsi_free_req(VirtIOSCSIReq *req)
> {
> qemu_iovec_destroy(&req->resp_iov);
> qemu_sglist_destroy(&req->qsgl);
> - g_free(req);
> + g_slice_free(VirtIOSCSIReq, req);
> }
>
> static void virtio_scsi_complete_req(VirtIOSCSIReq *req)
> @@ -532,7 +534,8 @@ static void virtio_scsi_set_config(VirtIODevice *vdev,
> VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
>
> if ((uint32_t) virtio_ldl_p(vdev, &scsiconf->sense_size) >= 65536 ||
> - (uint32_t) virtio_ldl_p(vdev, &scsiconf->cdb_size) >= 256) {
> + (uint32_t) virtio_ldl_p(vdev, &scsiconf->cdb_size)
> + >= VIRTIO_SCSI_CDB_SIZE_MAX) {
> error_report("bad data written to virtio-scsi configuration space");
> exit(1);
> }
> diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
> index 188a2d9..6e876f4 100644
> --- a/include/hw/virtio/virtio-scsi.h
> +++ b/include/hw/virtio/virtio-scsi.h
> @@ -37,6 +37,7 @@
>
> #define VIRTIO_SCSI_VQ_SIZE 128
> #define VIRTIO_SCSI_CDB_SIZE 32
> +#define VIRTIO_SCSI_CDB_SIZE_MAX 256
> #define VIRTIO_SCSI_SENSE_SIZE 96
> #define VIRTIO_SCSI_MAX_CHANNEL 0
> #define VIRTIO_SCSI_MAX_TARGET 255
>
