| Message ID | 1355833972-20319-3-git-send-email-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Il 18/12/2012 14:37, Michael S. Tsirkin ha scritto: > On Tue, Dec 18, 2012 at 01:32:49PM +0100, Paolo Bonzini wrote: >> Using the new virtio_scsi_add_sg function lets us simplify the queueing >> path. In particular, all data protected by the tgt_lock is just gone >> (multiqueue will find a new use for the lock). > > vq access still needs some protection: virtio is not reentrant > by itself. with tgt_lock gone what protects vq against > concurrent add_buf calls? vq_lock. Paolo >> The speedup is relatively small (2-4%) but it is worthwhile because of >> the code simplification---both in this patches and in the next ones. >> >> Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> >> --- >> v1->v2: new >> >> drivers/scsi/virtio_scsi.c | 94 +++++++++++++++++++------------------------ >> 1 files changed, 42 insertions(+), 52 deletions(-) >> >> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c >> index 74ab67a..2b93b6e 100644 >> --- a/drivers/scsi/virtio_scsi.c >> +++ b/drivers/scsi/virtio_scsi.c >> @@ -59,11 +59,8 @@ struct virtio_scsi_vq { >> >> /* Per-target queue state */ >> struct virtio_scsi_target_state { >> - /* Protects sg. Lock hierarchy is tgt_lock -> vq_lock. */ >> + /* Never held at the same time as vq_lock. */ >> spinlock_t tgt_lock; >> - >> - /* For sglist construction when adding commands to the virtqueue. */ >> - struct scatterlist sg[]; >> }; >> >> /* Driver instance state */ >> @@ -351,57 +348,58 @@ static void virtscsi_event_done(struct virtqueue *vq) >> spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags); >> }; >> >> -static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx, >> - struct scsi_data_buffer *sdb) >> -{ >> - struct sg_table *table = &sdb->table; >> - struct scatterlist *sg_elem; >> - unsigned int idx = *p_idx; >> - int i; >> - >> - for_each_sg(table->sgl, sg_elem, table->nents, i) >> - sg[idx++] = *sg_elem; >> - >> - *p_idx = idx; >> -} >> - >> /** >> - * virtscsi_map_cmd - map a scsi_cmd to a virtqueue scatterlist >> + * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue >> * @vscsi : virtio_scsi state >> * @cmd : command structure >> - * @out_num : number of read-only elements >> - * @in_num : number of write-only elements >> * @req_size : size of the request buffer >> * @resp_size : size of the response buffer >> - * >> - * Called with tgt_lock held. >> + * @gfp : flags to use for memory allocations >> */ >> -static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt, >> - struct virtio_scsi_cmd *cmd, >> - unsigned *out_num, unsigned *in_num, >> - size_t req_size, size_t resp_size) >> +static int virtscsi_add_cmd(struct virtqueue *vq, >> + struct virtio_scsi_cmd *cmd, >> + size_t req_size, size_t resp_size, gfp_t gfp) >> { >> struct scsi_cmnd *sc = cmd->sc; >> - struct scatterlist *sg = tgt->sg; >> - unsigned int idx = 0; >> + struct scatterlist sg; >> + unsigned int count, count_sg; >> + struct sg_table *out, *in; >> + struct virtqueue_buf buf; >> + int ret; >> + >> + out = in = NULL; >> + >> + if (sc && sc->sc_data_direction != DMA_NONE) { >> + if (sc->sc_data_direction != DMA_FROM_DEVICE) >> + out = &scsi_out(sc)->table; >> + if (sc->sc_data_direction != DMA_TO_DEVICE) >> + in = &scsi_in(sc)->table; >> + } >> + >> + count_sg = 2 + (out ? 1 : 0) + (in ? 1 : 0); >> + count = 2 + (out ? out->nents : 0) + (in ? in->nents : 0); >> + ret = virtqueue_start_buf(vq, &buf, cmd, count, count_sg, gfp); >> + if (ret < 0) >> + return ret; >> >> /* Request header. */ >> - sg_set_buf(&sg[idx++], &cmd->req, req_size); >> + sg_init_one(&sg, &cmd->req, req_size); >> + virtqueue_add_sg(&buf, &sg, 1, DMA_TO_DEVICE); >> >> /* Data-out buffer. */ >> - if (sc && sc->sc_data_direction != DMA_FROM_DEVICE) >> - virtscsi_map_sgl(sg, &idx, scsi_out(sc)); >> - >> - *out_num = idx; >> + if (out) >> + virtqueue_add_sg(&buf, out->sgl, out->nents, DMA_TO_DEVICE); >> >> /* Response header. */ >> - sg_set_buf(&sg[idx++], &cmd->resp, resp_size); >> + sg_init_one(&sg, &cmd->resp, resp_size); >> + virtqueue_add_sg(&buf, &sg, 1, DMA_FROM_DEVICE); >> >> /* Data-in buffer */ >> - if (sc && sc->sc_data_direction != DMA_TO_DEVICE) >> - virtscsi_map_sgl(sg, &idx, scsi_in(sc)); >> + if (in) >> + virtqueue_add_sg(&buf, in->sgl, in->nents, DMA_FROM_DEVICE); >> >> - *in_num = idx - *out_num; >> + virtqueue_end_buf(&buf); >> + return 0; >> } >> >> static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt, >> @@ -409,25 +407,20 @@ static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt, >> struct virtio_scsi_cmd *cmd, >> size_t req_size, size_t resp_size, gfp_t gfp) >> { >> - unsigned int out_num, in_num; >> unsigned long flags; >> - int err; >> + int ret; >> bool needs_kick = false; >> >> - spin_lock_irqsave(&tgt->tgt_lock, flags); >> - virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size); >> - >> - spin_lock(&vq->vq_lock); >> - err = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp); >> - spin_unlock(&tgt->tgt_lock); >> - if (!err) >> + spin_lock_irqsave(&vq->vq_lock, flags); >> + ret = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size, gfp); >> + if (!ret) >> needs_kick = virtqueue_kick_prepare(vq->vq); >> >> spin_unlock_irqrestore(&vq->vq_lock, flags); >> >> if (needs_kick) >> virtqueue_notify(vq->vq); >> - return err; >> + return ret; >> } >> >> static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc) >> @@ -592,14 +585,11 @@ static struct virtio_scsi_target_state *virtscsi_alloc_tgt( >> gfp_t gfp_mask = GFP_KERNEL; >> >> /* We need extra sg elements at head and tail. */ >> - tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2), >> - gfp_mask); >> - >> + tgt = kmalloc(sizeof(*tgt), gfp_mask); >> if (!tgt) >> return NULL; >> >> spin_lock_init(&tgt->tgt_lock); >> - sg_init_table(tgt->sg, sg_elems + 2); >> return tgt; >> } >> >> -- >> 1.7.1 >> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Dec 18, 2012 at 01:32:49PM +0100, Paolo Bonzini wrote: > Using the new virtio_scsi_add_sg function lets us simplify the queueing > path. In particular, all data protected by the tgt_lock is just gone > (multiqueue will find a new use for the lock). vq access still needs some protection: virtio is not reentrant by itself. with tgt_lock gone what protects vq against concurrent add_buf calls? > The speedup is relatively small (2-4%) but it is worthwhile because of > the code simplification---both in this patches and in the next ones. > > Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > v1->v2: new > > drivers/scsi/virtio_scsi.c | 94 +++++++++++++++++++------------------------ > 1 files changed, 42 insertions(+), 52 deletions(-) > > diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c > index 74ab67a..2b93b6e 100644 > --- a/drivers/scsi/virtio_scsi.c > +++ b/drivers/scsi/virtio_scsi.c > @@ -59,11 +59,8 @@ struct virtio_scsi_vq { > > /* Per-target queue state */ > struct virtio_scsi_target_state { > - /* Protects sg. Lock hierarchy is tgt_lock -> vq_lock. */ > + /* Never held at the same time as vq_lock. */ > spinlock_t tgt_lock; > - > - /* For sglist construction when adding commands to the virtqueue. */ > - struct scatterlist sg[]; > }; > > /* Driver instance state */ > @@ -351,57 +348,58 @@ static void virtscsi_event_done(struct virtqueue *vq) > spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags); > }; > > -static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx, > - struct scsi_data_buffer *sdb) > -{ > - struct sg_table *table = &sdb->table; > - struct scatterlist *sg_elem; > - unsigned int idx = *p_idx; > - int i; > - > - for_each_sg(table->sgl, sg_elem, table->nents, i) > - sg[idx++] = *sg_elem; > - > - *p_idx = idx; > -} > - > /** > - * virtscsi_map_cmd - map a scsi_cmd to a virtqueue scatterlist > + * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue > * @vscsi : virtio_scsi state > * @cmd : command structure > - * @out_num : number of read-only elements > - * @in_num : number of write-only elements > * @req_size : size of the request buffer > * @resp_size : size of the response buffer > - * > - * Called with tgt_lock held. > + * @gfp : flags to use for memory allocations > */ > -static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt, > - struct virtio_scsi_cmd *cmd, > - unsigned *out_num, unsigned *in_num, > - size_t req_size, size_t resp_size) > +static int virtscsi_add_cmd(struct virtqueue *vq, > + struct virtio_scsi_cmd *cmd, > + size_t req_size, size_t resp_size, gfp_t gfp) > { > struct scsi_cmnd *sc = cmd->sc; > - struct scatterlist *sg = tgt->sg; > - unsigned int idx = 0; > + struct scatterlist sg; > + unsigned int count, count_sg; > + struct sg_table *out, *in; > + struct virtqueue_buf buf; > + int ret; > + > + out = in = NULL; > + > + if (sc && sc->sc_data_direction != DMA_NONE) { > + if (sc->sc_data_direction != DMA_FROM_DEVICE) > + out = &scsi_out(sc)->table; > + if (sc->sc_data_direction != DMA_TO_DEVICE) > + in = &scsi_in(sc)->table; > + } > + > + count_sg = 2 + (out ? 1 : 0) + (in ? 1 : 0); > + count = 2 + (out ? out->nents : 0) + (in ? in->nents : 0); > + ret = virtqueue_start_buf(vq, &buf, cmd, count, count_sg, gfp); > + if (ret < 0) > + return ret; > > /* Request header. */ > - sg_set_buf(&sg[idx++], &cmd->req, req_size); > + sg_init_one(&sg, &cmd->req, req_size); > + virtqueue_add_sg(&buf, &sg, 1, DMA_TO_DEVICE); > > /* Data-out buffer. */ > - if (sc && sc->sc_data_direction != DMA_FROM_DEVICE) > - virtscsi_map_sgl(sg, &idx, scsi_out(sc)); > - > - *out_num = idx; > + if (out) > + virtqueue_add_sg(&buf, out->sgl, out->nents, DMA_TO_DEVICE); > > /* Response header. */ > - sg_set_buf(&sg[idx++], &cmd->resp, resp_size); > + sg_init_one(&sg, &cmd->resp, resp_size); > + virtqueue_add_sg(&buf, &sg, 1, DMA_FROM_DEVICE); > > /* Data-in buffer */ > - if (sc && sc->sc_data_direction != DMA_TO_DEVICE) > - virtscsi_map_sgl(sg, &idx, scsi_in(sc)); > + if (in) > + virtqueue_add_sg(&buf, in->sgl, in->nents, DMA_FROM_DEVICE); > > - *in_num = idx - *out_num; > + virtqueue_end_buf(&buf); > + return 0; > } > > static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt, > @@ -409,25 +407,20 @@ static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt, > struct virtio_scsi_cmd *cmd, > size_t req_size, size_t resp_size, gfp_t gfp) > { > - unsigned int out_num, in_num; > unsigned long flags; > - int err; > + int ret; > bool needs_kick = false; > > - spin_lock_irqsave(&tgt->tgt_lock, flags); > - virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size); > - > - spin_lock(&vq->vq_lock); > - err = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp); > - spin_unlock(&tgt->tgt_lock); > - if (!err) > + spin_lock_irqsave(&vq->vq_lock, flags); > + ret = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size, gfp); > + if (!ret) > needs_kick = virtqueue_kick_prepare(vq->vq); > > spin_unlock_irqrestore(&vq->vq_lock, flags); > > if (needs_kick) > virtqueue_notify(vq->vq); > - return err; > + return ret; > } > > static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc) > @@ -592,14 +585,11 @@ static struct virtio_scsi_target_state *virtscsi_alloc_tgt( > gfp_t gfp_mask = GFP_KERNEL; > > /* We need extra sg elements at head and tail. */ > - tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2), > - gfp_mask); > - > + tgt = kmalloc(sizeof(*tgt), gfp_mask); > if (!tgt) > return NULL; > > spin_lock_init(&tgt->tgt_lock); > - sg_init_table(tgt->sg, sg_elems + 2); > return tgt; > } > > -- > 1.7.1 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c index 74ab67a..2b93b6e 100644 --- a/drivers/scsi/virtio_scsi.c +++ b/drivers/scsi/virtio_scsi.c @@ -59,11 +59,8 @@ struct virtio_scsi_vq { /* Per-target queue state */ struct virtio_scsi_target_state { - /* Protects sg. Lock hierarchy is tgt_lock -> vq_lock. */ + /* Never held at the same time as vq_lock. */ spinlock_t tgt_lock; - - /* For sglist construction when adding commands to the virtqueue. */ - struct scatterlist sg[]; }; /* Driver instance state */ @@ -351,57 +348,58 @@ static void virtscsi_event_done(struct virtqueue *vq) spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags); }; -static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx, - struct scsi_data_buffer *sdb) -{ - struct sg_table *table = &sdb->table; - struct scatterlist *sg_elem; - unsigned int idx = *p_idx; - int i; - - for_each_sg(table->sgl, sg_elem, table->nents, i) - sg[idx++] = *sg_elem; - - *p_idx = idx; -} - /** - * virtscsi_map_cmd - map a scsi_cmd to a virtqueue scatterlist + * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue * @vscsi : virtio_scsi state * @cmd : command structure - * @out_num : number of read-only elements - * @in_num : number of write-only elements * @req_size : size of the request buffer * @resp_size : size of the response buffer - * - * Called with tgt_lock held. + * @gfp : flags to use for memory allocations */ -static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt, - struct virtio_scsi_cmd *cmd, - unsigned *out_num, unsigned *in_num, - size_t req_size, size_t resp_size) +static int virtscsi_add_cmd(struct virtqueue *vq, + struct virtio_scsi_cmd *cmd, + size_t req_size, size_t resp_size, gfp_t gfp) { struct scsi_cmnd *sc = cmd->sc; - struct scatterlist *sg = tgt->sg; - unsigned int idx = 0; + struct scatterlist sg; + unsigned int count, count_sg; + struct sg_table *out, *in; + struct virtqueue_buf buf; + int ret; + + out = in = NULL; + + if (sc && sc->sc_data_direction != DMA_NONE) { + if (sc->sc_data_direction != DMA_FROM_DEVICE) + out = &scsi_out(sc)->table; + if (sc->sc_data_direction != DMA_TO_DEVICE) + in = &scsi_in(sc)->table; + } + + count_sg = 2 + (out ? 1 : 0) + (in ? 1 : 0); + count = 2 + (out ? out->nents : 0) + (in ? in->nents : 0); + ret = virtqueue_start_buf(vq, &buf, cmd, count, count_sg, gfp); + if (ret < 0) + return ret; /* Request header. */ - sg_set_buf(&sg[idx++], &cmd->req, req_size); + sg_init_one(&sg, &cmd->req, req_size); + virtqueue_add_sg(&buf, &sg, 1, DMA_TO_DEVICE); /* Data-out buffer. */ - if (sc && sc->sc_data_direction != DMA_FROM_DEVICE) - virtscsi_map_sgl(sg, &idx, scsi_out(sc)); - - *out_num = idx; + if (out) + virtqueue_add_sg(&buf, out->sgl, out->nents, DMA_TO_DEVICE); /* Response header. */ - sg_set_buf(&sg[idx++], &cmd->resp, resp_size); + sg_init_one(&sg, &cmd->resp, resp_size); + virtqueue_add_sg(&buf, &sg, 1, DMA_FROM_DEVICE); /* Data-in buffer */ - if (sc && sc->sc_data_direction != DMA_TO_DEVICE) - virtscsi_map_sgl(sg, &idx, scsi_in(sc)); + if (in) + virtqueue_add_sg(&buf, in->sgl, in->nents, DMA_FROM_DEVICE); - *in_num = idx - *out_num; + virtqueue_end_buf(&buf); + return 0; } static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt, @@ -409,25 +407,20 @@ static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt, struct virtio_scsi_cmd *cmd, size_t req_size, size_t resp_size, gfp_t gfp) { - unsigned int out_num, in_num; unsigned long flags; - int err; + int ret; bool needs_kick = false; - spin_lock_irqsave(&tgt->tgt_lock, flags); - virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size); - - spin_lock(&vq->vq_lock); - err = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp); - spin_unlock(&tgt->tgt_lock); - if (!err) + spin_lock_irqsave(&vq->vq_lock, flags); + ret = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size, gfp); + if (!ret) needs_kick = virtqueue_kick_prepare(vq->vq); spin_unlock_irqrestore(&vq->vq_lock, flags); if (needs_kick) virtqueue_notify(vq->vq); - return err; + return ret; } static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc) @@ -592,14 +585,11 @@ static struct virtio_scsi_target_state *virtscsi_alloc_tgt( gfp_t gfp_mask = GFP_KERNEL; /* We need extra sg elements at head and tail. */ - tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2), - gfp_mask); - + tgt = kmalloc(sizeof(*tgt), gfp_mask); if (!tgt) return NULL; spin_lock_init(&tgt->tgt_lock); - sg_init_table(tgt->sg, sg_elems + 2); return tgt; }