This series implements virtio-scsi queue steering, which gives
performance improvements of up to 50% (measured both with QEMU and
tcm_vhost backends).
This version rebased on Rusty's virtio ring rework patches, which
has already gone into virtio-next today.
We hope this can go into virtio-next together with the virtio ring
rework pathes.
V7: respin to fix the patch apply error
V6: rework "redo allocation of target data" (James)
fix comments (Venkatesh)
rebase to virtio-next
V5: improving the grammar of 1/5 (Paolo)
move the dropping of sg_elems to 'virtio-scsi: use virtqueue_add_sgs for
command buffers'. (Asias)
V4: rebase on virtio ring rework patches (rusty's pending-rebases branch)
V3 and be found
http://marc.info/?l=linux-virtualization&m=136067440717154&w=2
It would probably be easier to get it in via Rusty's tree
because of the prerequisites. James, can we get your Acked-by?
Paolo Bonzini (3):
virtio-scsi: pass struct virtio_scsi to virtqueue completion function
virtio-scsi: push vq lock/unlock into virtscsi_vq_done
virtio-scsi: introduce multiqueue support
Wanlong Gao (2):
virtio-scsi: redo allocation of target data
virtio-scsi: reset virtqueue affinity when doing cpu hotplug
drivers/scsi/virtio_scsi.c | 387 ++++++++++++++++++++++++++++++++++++---------
1 file changed, 309 insertions(+), 78 deletions(-)
--
1.8.2.rc2
Wanlong Gao
2013-Mar-23 11:28 UTC
[PATCH V7 1/5] virtio-scsi: redo allocation of target data
virtio_scsi_target_state is now empty. We will find new uses for it in
the next few patches, so this patch does not drop it completely.
And as James suggested, we use entries target_alloc and target_destroy
in the host template to allocate and destroy the virtio_scsi_target_state
of each target, attach this struct to scsi_target->hostdata. Now
we can get at it from the sdev with scsi_target(sdev)->hostdata.
No messing around with fixed size arrays and bulk memory allocation
and no need to pass in the maximum target size as a parameter because
everything should now happen dynamically.
Cc: James Bottomley <James.Bottomley at HansenPartnership.com>
Cc: linux-scsi at vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Reviewed-by: Asias He <asias at redhat.com>
---
drivers/scsi/virtio_scsi.c | 71 ++++++++++++++++------------------------------
1 file changed, 25 insertions(+), 46 deletions(-)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index b53ba9e..ffa03e8 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -75,8 +75,6 @@ struct virtio_scsi {
/* Get some buffers ready for event vq */
struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
-
- struct virtio_scsi_target_state *tgt[];
};
static struct kmem_cache *virtscsi_cmd_cache;
@@ -530,6 +528,25 @@ static int virtscsi_abort(struct scsi_cmnd *sc)
return virtscsi_tmf(vscsi, cmd);
}
+static int virtscsi_target_alloc(struct scsi_target *starget)
+{
+ struct virtio_scsi_target_state *tgt + kmalloc(sizeof(*tgt), GFP_KERNEL);
+ if (!tgt)
+ return -ENOMEM;
+
+ spin_lock_init(&tgt->tgt_lock);
+
+ starget->hostdata = tgt;
+ return 0;
+}
+
+static void virtscsi_target_destroy(struct scsi_target *starget)
+{
+ struct virtio_scsi_target_state *tgt = starget->hostdata;
+ kfree(tgt);
+}
+
static struct scsi_host_template virtscsi_host_template = {
.module = THIS_MODULE,
.name = "Virtio SCSI HBA",
@@ -542,6 +559,8 @@ static struct scsi_host_template virtscsi_host_template = {
.can_queue = 1024,
.dma_boundary = UINT_MAX,
.use_clustering = ENABLE_CLUSTERING,
+ .target_alloc = virtscsi_target_alloc,
+ .target_destroy = virtscsi_target_destroy,
};
#define virtscsi_config_get(vdev, fld) \
@@ -568,20 +587,6 @@ static void virtscsi_init_vq(struct virtio_scsi_vq
*virtscsi_vq,
virtscsi_vq->vq = vq;
}
-static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
- struct virtio_device *vdev)
-{
- struct virtio_scsi_target_state *tgt;
- gfp_t gfp_mask = GFP_KERNEL;
-
- tgt = kmalloc(sizeof(*tgt), gfp_mask);
- if (!tgt)
- return NULL;
-
- spin_lock_init(&tgt->tgt_lock);
- return tgt;
-}
-
static void virtscsi_scan(struct virtio_device *vdev)
{
struct Scsi_Host *shost = (struct Scsi_Host *)vdev->priv;
@@ -591,28 +596,17 @@ static void virtscsi_scan(struct virtio_device *vdev)
static void virtscsi_remove_vqs(struct virtio_device *vdev)
{
- struct Scsi_Host *sh = virtio_scsi_host(vdev);
- struct virtio_scsi *vscsi = shost_priv(sh);
- u32 i, num_targets;
-
/* Stop all the virtqueues. */
vdev->config->reset(vdev);
- num_targets = sh->max_id;
- for (i = 0; i < num_targets; i++) {
- kfree(vscsi->tgt[i]);
- vscsi->tgt[i] = NULL;
- }
-
vdev->config->del_vqs(vdev);
}
static int virtscsi_init(struct virtio_device *vdev,
- struct virtio_scsi *vscsi, int num_targets)
+ struct virtio_scsi *vscsi)
{
int err;
struct virtqueue *vqs[3];
- u32 i;
vq_callback_t *callbacks[] = {
virtscsi_ctrl_done,
@@ -640,18 +634,6 @@ static int virtscsi_init(struct virtio_device *vdev,
if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
virtscsi_kick_event_all(vscsi);
- for (i = 0; i < num_targets; i++) {
- vscsi->tgt[i] = virtscsi_alloc_tgt(vdev);
- if (!vscsi->tgt[i]) {
- err = -ENOMEM;
- goto out;
- }
- }
- err = 0;
-
-out:
- if (err)
- virtscsi_remove_vqs(vdev);
return err;
}
@@ -663,12 +645,9 @@ static int virtscsi_probe(struct virtio_device *vdev)
u32 sg_elems, num_targets;
u32 cmd_per_lun;
- /* Allocate memory and link the structs together. */
num_targets = virtscsi_config_get(vdev, max_target) + 1;
- shost = scsi_host_alloc(&virtscsi_host_template,
- sizeof(*vscsi)
- + num_targets * sizeof(struct virtio_scsi_target_state));
+ shost = scsi_host_alloc(&virtscsi_host_template, sizeof(*vscsi));
if (!shost)
return -ENOMEM;
@@ -678,7 +657,7 @@ static int virtscsi_probe(struct virtio_device *vdev)
vscsi->vdev = vdev;
vdev->priv = shost;
- err = virtscsi_init(vdev, vscsi, num_targets);
+ err = virtscsi_init(vdev, vscsi);
if (err)
goto virtscsi_init_failed;
@@ -735,7 +714,7 @@ static int virtscsi_restore(struct virtio_device *vdev)
struct Scsi_Host *sh = virtio_scsi_host(vdev);
struct virtio_scsi *vscsi = shost_priv(sh);
- return virtscsi_init(vdev, vscsi, sh->max_id);
+ return virtscsi_init(vdev, vscsi);
}
#endif
--
1.8.2.rc2
Wanlong Gao
2013-Mar-23 11:28 UTC
[PATCH V7 2/5] virtio-scsi: pass struct virtio_scsi to virtqueue completion function
From: Paolo Bonzini <pbonzini at redhat.com>
This will be needed soon in order to retrieve the per-target
struct.
Cc: linux-scsi at vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Reviewed-by: Asias He <asias at redhat.com>
---
drivers/scsi/virtio_scsi.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index ffa03e8..c23560c 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -104,7 +104,7 @@ static void virtscsi_compute_resid(struct scsi_cmnd *sc, u32
resid)
*
* Called with vq_lock held.
*/
-static void virtscsi_complete_cmd(void *buf)
+static void virtscsi_complete_cmd(struct virtio_scsi *vscsi, void *buf)
{
struct virtio_scsi_cmd *cmd = buf;
struct scsi_cmnd *sc = cmd->sc;
@@ -165,7 +165,8 @@ static void virtscsi_complete_cmd(void *buf)
sc->scsi_done(sc);
}
-static void virtscsi_vq_done(struct virtqueue *vq, void (*fn)(void *buf))
+static void virtscsi_vq_done(struct virtio_scsi *vscsi, struct virtqueue *vq,
+ void (*fn)(struct virtio_scsi *vscsi, void *buf))
{
void *buf;
unsigned int len;
@@ -173,7 +174,7 @@ static void virtscsi_vq_done(struct virtqueue *vq, void
(*fn)(void *buf))
do {
virtqueue_disable_cb(vq);
while ((buf = virtqueue_get_buf(vq, &len)) != NULL)
- fn(buf);
+ fn(vscsi, buf);
} while (!virtqueue_enable_cb(vq));
}
@@ -184,11 +185,11 @@ static void virtscsi_req_done(struct virtqueue *vq)
unsigned long flags;
spin_lock_irqsave(&vscsi->req_vq.vq_lock, flags);
- virtscsi_vq_done(vq, virtscsi_complete_cmd);
+ virtscsi_vq_done(vscsi, vq, virtscsi_complete_cmd);
spin_unlock_irqrestore(&vscsi->req_vq.vq_lock, flags);
};
-static void virtscsi_complete_free(void *buf)
+static void virtscsi_complete_free(struct virtio_scsi *vscsi, void *buf)
{
struct virtio_scsi_cmd *cmd = buf;
@@ -205,7 +206,7 @@ static void virtscsi_ctrl_done(struct virtqueue *vq)
unsigned long flags;
spin_lock_irqsave(&vscsi->ctrl_vq.vq_lock, flags);
- virtscsi_vq_done(vq, virtscsi_complete_free);
+ virtscsi_vq_done(vscsi, vq, virtscsi_complete_free);
spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
};
@@ -329,7 +330,7 @@ static void virtscsi_handle_event(struct work_struct *work)
virtscsi_kick_event(vscsi, event_node);
}
-static void virtscsi_complete_event(void *buf)
+static void virtscsi_complete_event(struct virtio_scsi *vscsi, void *buf)
{
struct virtio_scsi_event_node *event_node = buf;
@@ -344,7 +345,7 @@ static void virtscsi_event_done(struct virtqueue *vq)
unsigned long flags;
spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
- virtscsi_vq_done(vq, virtscsi_complete_event);
+ virtscsi_vq_done(vscsi, vq, virtscsi_complete_event);
spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
};
--
1.8.2.rc2
Wanlong Gao
2013-Mar-23 11:28 UTC
[PATCH V7 3/5] virtio-scsi: push vq lock/unlock into virtscsi_vq_done
From: Paolo Bonzini <pbonzini at redhat.com>
Avoid duplicated code in all of the callers.
Cc: linux-scsi at vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Reviewed-by: Asias He <asias at redhat.com>
---
drivers/scsi/virtio_scsi.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index c23560c..dc2daec 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -165,28 +165,30 @@ static void virtscsi_complete_cmd(struct virtio_scsi
*vscsi, void *buf)
sc->scsi_done(sc);
}
-static void virtscsi_vq_done(struct virtio_scsi *vscsi, struct virtqueue *vq,
+static void virtscsi_vq_done(struct virtio_scsi *vscsi,
+ struct virtio_scsi_vq *virtscsi_vq,
void (*fn)(struct virtio_scsi *vscsi, void *buf))
{
void *buf;
unsigned int len;
+ unsigned long flags;
+ struct virtqueue *vq = virtscsi_vq->vq;
+ spin_lock_irqsave(&virtscsi_vq->vq_lock, flags);
do {
virtqueue_disable_cb(vq);
while ((buf = virtqueue_get_buf(vq, &len)) != NULL)
fn(vscsi, buf);
} while (!virtqueue_enable_cb(vq));
+ spin_unlock_irqrestore(&virtscsi_vq->vq_lock, flags);
}
static void virtscsi_req_done(struct virtqueue *vq)
{
struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
struct virtio_scsi *vscsi = shost_priv(sh);
- unsigned long flags;
- spin_lock_irqsave(&vscsi->req_vq.vq_lock, flags);
- virtscsi_vq_done(vscsi, vq, virtscsi_complete_cmd);
- spin_unlock_irqrestore(&vscsi->req_vq.vq_lock, flags);
+ virtscsi_vq_done(vscsi, &vscsi->req_vq, virtscsi_complete_cmd);
};
static void virtscsi_complete_free(struct virtio_scsi *vscsi, void *buf)
@@ -203,11 +205,8 @@ static void virtscsi_ctrl_done(struct virtqueue *vq)
{
struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
struct virtio_scsi *vscsi = shost_priv(sh);
- unsigned long flags;
- spin_lock_irqsave(&vscsi->ctrl_vq.vq_lock, flags);
- virtscsi_vq_done(vscsi, vq, virtscsi_complete_free);
- spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
+ virtscsi_vq_done(vscsi, &vscsi->ctrl_vq, virtscsi_complete_free);
};
static int virtscsi_kick_event(struct virtio_scsi *vscsi,
@@ -342,11 +341,8 @@ static void virtscsi_event_done(struct virtqueue *vq)
{
struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
struct virtio_scsi *vscsi = shost_priv(sh);
- unsigned long flags;
- spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
- virtscsi_vq_done(vscsi, vq, virtscsi_complete_event);
- spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
+ virtscsi_vq_done(vscsi, &vscsi->event_vq, virtscsi_complete_event);
};
/**
--
1.8.2.rc2
Wanlong Gao
2013-Mar-23 11:28 UTC
[PATCH V7 4/5] virtio-scsi: introduce multiqueue support
From: Paolo Bonzini <pbonzini at redhat.com>
This patch adds queue steering to virtio-scsi. When a target is sent
multiple requests, we always drive them to the same queue so that FIFO
processing order is kept. However, if a target was idle, we can choose
a queue arbitrarily. In this case the queue is chosen according to the
current VCPU, so the driver expects the number of request queues to be
equal to the number of VCPUs. This makes it easy and fast to select
the queue, and also lets the driver optimize the IRQ affinity for the
virtqueues (each virtqueue's affinity is set to the CPU that
"owns"
the queue).
The speedup comes from improving cache locality and giving CPU affinity
to the virtqueues, which is why this scheme was selected. Assuming that
the thread that is sending requests to the device is I/O-bound, it is
likely to be sleeping at the time the ISR is executed, and thus executing
the ISR on the same processor that sent the requests is cheap.
However, the kernel will not execute the ISR on the "best" processor
unless you explicitly set the affinity. This is because in practice
you will have many such I/O-bound processes and thus many otherwise
idle processors. Then the kernel will execute the ISR on a random
processor, rather than the one that is sending requests to the device.
The alternative to per-CPU virtqueues is per-target virtqueues. To
achieve the same locality, we could dynamically choose the virtqueue's
affinity based on the CPU of the last task that sent a request. This
is less appealing because we do not set the affinity directly---we only
provide a hint to the irqbalanced running in userspace. Dynamically
changing the affinity only works if the userspace applies the hint
fast enough.
Cc: linux-scsi at vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Reviewed-by: Asias He <asias at redhat.com>
Tested-by: Venkatesh Srinivas <venkateshs at google.com>
---
drivers/scsi/virtio_scsi.c | 282 ++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 254 insertions(+), 28 deletions(-)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index dc2daec..8dcdef0 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -22,12 +22,14 @@
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
#include <linux/virtio_scsi.h>
+#include <linux/cpu.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>
#define VIRTIO_SCSI_MEMPOOL_SZ 64
#define VIRTIO_SCSI_EVENT_LEN 8
+#define VIRTIO_SCSI_VQ_BASE 2
/* Command queue element */
struct virtio_scsi_cmd {
@@ -59,22 +61,58 @@ struct virtio_scsi_vq {
struct virtqueue *vq;
};
-/* Per-target queue state */
+/*
+ * Per-target queue state.
+ *
+ * This struct holds the data needed by the queue steering policy. When a
+ * target is sent multiple requests, we need to drive them to the same queue so
+ * that FIFO processing order is kept. However, if a target was idle, we can
+ * choose a queue arbitrarily. In this case the queue is chosen according to
+ * the current VCPU, so the driver expects the number of request queues to be
+ * equal to the number of VCPUs. This makes it easy and fast to select the
+ * queue, and also lets the driver optimize the IRQ affinity for the virtqueues
+ * (each virtqueue's affinity is set to the CPU that "owns" the
queue).
+ *
+ * An interesting effect of this policy is that only writes to req_vq need to
+ * take the tgt_lock. Read can be done outside the lock because:
+ *
+ * - writes of req_vq only occur when atomic_inc_return(&tgt->reqs)
returns 1.
+ * In that case, no other CPU is reading req_vq: even if they were in
+ * virtscsi_queuecommand_multi, they would be spinning on tgt_lock.
+ *
+ * - reads of req_vq only occur when the target is not idle (reqs != 0).
+ * A CPU that enters virtscsi_queuecommand_multi will not modify req_vq.
+ *
+ * Similarly, decrements of reqs are never concurrent with writes of req_vq.
+ * Thus they can happen outside the tgt_lock, provided of course we make reqs
+ * an atomic_t.
+ */
struct virtio_scsi_target_state {
- /* Never held at the same time as vq_lock. */
+ /* This spinlock never held at the same time as vq_lock. */
spinlock_t tgt_lock;
+
+ /* Count of outstanding requests. */
+ atomic_t reqs;
+
+ /* Currently active virtqueue for requests sent to this target. */
+ struct virtio_scsi_vq *req_vq;
};
/* Driver instance state */
struct virtio_scsi {
struct virtio_device *vdev;
- struct virtio_scsi_vq ctrl_vq;
- struct virtio_scsi_vq event_vq;
- struct virtio_scsi_vq req_vq;
-
/* Get some buffers ready for event vq */
struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];
+
+ u32 num_queues;
+
+ /* If the affinity hint is set for virtqueues */
+ bool affinity_hint_set;
+
+ struct virtio_scsi_vq ctrl_vq;
+ struct virtio_scsi_vq event_vq;
+ struct virtio_scsi_vq req_vqs[];
};
static struct kmem_cache *virtscsi_cmd_cache;
@@ -109,6 +147,8 @@ static void virtscsi_complete_cmd(struct virtio_scsi *vscsi,
void *buf)
struct virtio_scsi_cmd *cmd = buf;
struct scsi_cmnd *sc = cmd->sc;
struct virtio_scsi_cmd_resp *resp = &cmd->resp.cmd;
+ struct virtio_scsi_target_state *tgt +
scsi_target(sc->device)->hostdata;
dev_dbg(&sc->device->sdev_gendev,
"cmd %p response %u status %#02x sense_len %u\n",
@@ -163,6 +203,8 @@ static void virtscsi_complete_cmd(struct virtio_scsi *vscsi,
void *buf)
mempool_free(cmd, virtscsi_cmd_pool);
sc->scsi_done(sc);
+
+ atomic_dec(&tgt->reqs);
}
static void virtscsi_vq_done(struct virtio_scsi *vscsi,
@@ -187,8 +229,42 @@ static void virtscsi_req_done(struct virtqueue *vq)
{
struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
struct virtio_scsi *vscsi = shost_priv(sh);
+ int index = vq->index - VIRTIO_SCSI_VQ_BASE;
+ struct virtio_scsi_vq *req_vq = &vscsi->req_vqs[index];
- virtscsi_vq_done(vscsi, &vscsi->req_vq, virtscsi_complete_cmd);
+ /*
+ * Read req_vq before decrementing the reqs field in
+ * virtscsi_complete_cmd.
+ *
+ * With barriers:
+ *
+ * CPU #0 virtscsi_queuecommand_multi (CPU #1)
+ * ------------------------------------------------------------
+ * lock vq_lock
+ * read req_vq
+ * read reqs (reqs = 1)
+ * write reqs (reqs = 0)
+ * increment reqs (reqs = 1)
+ * write req_vq
+ *
+ * Possible reordering without barriers:
+ *
+ * CPU #0 virtscsi_queuecommand_multi (CPU #1)
+ * ------------------------------------------------------------
+ * lock vq_lock
+ * read reqs (reqs = 1)
+ * write reqs (reqs = 0)
+ * increment reqs (reqs = 1)
+ * write req_vq
+ * read (wrong) req_vq
+ *
+ * We do not need a full smp_rmb, because req_vq is required to get
+ * to tgt->reqs: tgt is &vscsi->tgt[sc->device->id], where sc
is stored
+ * in the virtqueue as the user token.
+ */
+ smp_read_barrier_depends();
+
+ virtscsi_vq_done(vscsi, req_vq, virtscsi_complete_cmd);
};
static void virtscsi_complete_free(struct virtio_scsi *vscsi, void *buf)
@@ -251,7 +327,7 @@ static void virtscsi_cancel_event_work(struct virtio_scsi
*vscsi)
}
static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
- struct virtio_scsi_event *event)
+ struct virtio_scsi_event *event)
{
struct scsi_device *sdev;
struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
@@ -410,9 +486,10 @@ static int virtscsi_kick_cmd(struct virtio_scsi_vq *vq,
return err;
}
-static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
+static int virtscsi_queuecommand(struct virtio_scsi *vscsi,
+ struct virtio_scsi_vq *req_vq,
+ struct scsi_cmnd *sc)
{
- struct virtio_scsi *vscsi = shost_priv(sh);
struct virtio_scsi_cmd *cmd;
int ret;
@@ -446,7 +523,7 @@ static int virtscsi_queuecommand(struct Scsi_Host *sh,
struct scsi_cmnd *sc)
BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);
- if (virtscsi_kick_cmd(&vscsi->req_vq, cmd,
+ if (virtscsi_kick_cmd(req_vq, cmd,
sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
GFP_ATOMIC) == 0)
ret = 0;
@@ -457,6 +534,55 @@ out:
return ret;
}
+static int virtscsi_queuecommand_single(struct Scsi_Host *sh,
+ struct scsi_cmnd *sc)
+{
+ struct virtio_scsi *vscsi = shost_priv(sh);
+ struct virtio_scsi_target_state *tgt +
scsi_target(sc->device)->hostdata;
+
+ atomic_inc(&tgt->reqs);
+ return virtscsi_queuecommand(vscsi, &vscsi->req_vqs[0], sc);
+}
+
+static struct virtio_scsi_vq *virtscsi_pick_vq(struct virtio_scsi *vscsi,
+ struct virtio_scsi_target_state *tgt)
+{
+ struct virtio_scsi_vq *vq;
+ unsigned long flags;
+ u32 queue_num;
+
+ spin_lock_irqsave(&tgt->tgt_lock, flags);
+
+ /*
+ * The memory barrier after atomic_inc_return matches
+ * the smp_read_barrier_depends() in virtscsi_req_done.
+ */
+ if (atomic_inc_return(&tgt->reqs) > 1)
+ vq = ACCESS_ONCE(tgt->req_vq);
+ else {
+ queue_num = smp_processor_id();
+ while (unlikely(queue_num >= vscsi->num_queues))
+ queue_num -= vscsi->num_queues;
+
+ tgt->req_vq = vq = &vscsi->req_vqs[queue_num];
+ }
+
+ spin_unlock_irqrestore(&tgt->tgt_lock, flags);
+ return vq;
+}
+
+static int virtscsi_queuecommand_multi(struct Scsi_Host *sh,
+ struct scsi_cmnd *sc)
+{
+ struct virtio_scsi *vscsi = shost_priv(sh);
+ struct virtio_scsi_target_state *tgt +
scsi_target(sc->device)->hostdata;
+ struct virtio_scsi_vq *req_vq = virtscsi_pick_vq(vscsi, tgt);
+
+ return virtscsi_queuecommand(vscsi, req_vq, sc);
+}
+
static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
{
DECLARE_COMPLETION_ONSTACK(comp);
@@ -533,6 +659,8 @@ static int virtscsi_target_alloc(struct scsi_target
*starget)
return -ENOMEM;
spin_lock_init(&tgt->tgt_lock);
+ atomic_set(&tgt->reqs, 0);
+ tgt->req_vq = NULL;
starget->hostdata = tgt;
return 0;
@@ -544,12 +672,28 @@ static void virtscsi_target_destroy(struct scsi_target
*starget)
kfree(tgt);
}
-static struct scsi_host_template virtscsi_host_template = {
+static struct scsi_host_template virtscsi_host_template_single = {
.module = THIS_MODULE,
.name = "Virtio SCSI HBA",
.proc_name = "virtio_scsi",
- .queuecommand = virtscsi_queuecommand,
.this_id = -1,
+ .queuecommand = virtscsi_queuecommand_single,
+ .eh_abort_handler = virtscsi_abort,
+ .eh_device_reset_handler = virtscsi_device_reset,
+
+ .can_queue = 1024,
+ .dma_boundary = UINT_MAX,
+ .use_clustering = ENABLE_CLUSTERING,
+ .target_alloc = virtscsi_target_alloc,
+ .target_destroy = virtscsi_target_destroy,
+};
+
+static struct scsi_host_template virtscsi_host_template_multi = {
+ .module = THIS_MODULE,
+ .name = "Virtio SCSI HBA",
+ .proc_name = "virtio_scsi",
+ .this_id = -1,
+ .queuecommand = virtscsi_queuecommand_multi,
.eh_abort_handler = virtscsi_abort,
.eh_device_reset_handler = virtscsi_device_reset,
@@ -577,6 +721,47 @@ static struct scsi_host_template virtscsi_host_template = {
&__val, sizeof(__val)); \
})
+static void __virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
+{
+ int i;
+ int cpu;
+
+ /* In multiqueue mode, when the number of cpu is equal
+ * to the number of request queues, we let the qeueues
+ * to be private to one cpu by setting the affinity hint
+ * to eliminate the contention.
+ */
+ if ((vscsi->num_queues == 1 ||
+ vscsi->num_queues != num_online_cpus()) && affinity) {
+ if (vscsi->affinity_hint_set)
+ affinity = false;
+ else
+ return;
+ }
+
+ if (affinity) {
+ i = 0;
+ for_each_online_cpu(cpu) {
+ virtqueue_set_affinity(vscsi->req_vqs[i].vq, cpu);
+ i++;
+ }
+
+ vscsi->affinity_hint_set = true;
+ } else {
+ for (i = 0; i < vscsi->num_queues - VIRTIO_SCSI_VQ_BASE; i++)
+ virtqueue_set_affinity(vscsi->req_vqs[i].vq, -1);
+
+ vscsi->affinity_hint_set = false;
+ }
+}
+
+static void virtscsi_set_affinity(struct virtio_scsi *vscsi, bool affinity)
+{
+ get_online_cpus();
+ __virtscsi_set_affinity(vscsi, affinity);
+ put_online_cpus();
+}
+
static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
struct virtqueue *vq)
{
@@ -593,6 +778,11 @@ static void virtscsi_scan(struct virtio_device *vdev)
static void virtscsi_remove_vqs(struct virtio_device *vdev)
{
+ struct Scsi_Host *sh = virtio_scsi_host(vdev);
+ struct virtio_scsi *vscsi = shost_priv(sh);
+
+ virtscsi_set_affinity(vscsi, false);
+
/* Stop all the virtqueues. */
vdev->config->reset(vdev);
@@ -603,27 +793,43 @@ static int virtscsi_init(struct virtio_device *vdev,
struct virtio_scsi *vscsi)
{
int err;
- struct virtqueue *vqs[3];
+ u32 i;
+ u32 num_vqs;
+ vq_callback_t **callbacks;
+ const char **names;
+ struct virtqueue **vqs;
+
+ num_vqs = vscsi->num_queues + VIRTIO_SCSI_VQ_BASE;
+ vqs = kmalloc(num_vqs * sizeof(struct virtqueue *), GFP_KERNEL);
+ callbacks = kmalloc(num_vqs * sizeof(vq_callback_t *), GFP_KERNEL);
+ names = kmalloc(num_vqs * sizeof(char *), GFP_KERNEL);
+
+ if (!callbacks || !vqs || !names) {
+ err = -ENOMEM;
+ goto out;
+ }
- vq_callback_t *callbacks[] = {
- virtscsi_ctrl_done,
- virtscsi_event_done,
- virtscsi_req_done
- };
- const char *names[] = {
- "control",
- "event",
- "request"
- };
+ callbacks[0] = virtscsi_ctrl_done;
+ callbacks[1] = virtscsi_event_done;
+ names[0] = "control";
+ names[1] = "event";
+ for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++) {
+ callbacks[i] = virtscsi_req_done;
+ names[i] = "request";
+ }
/* Discover virtqueues and write information to configuration. */
- err = vdev->config->find_vqs(vdev, 3, vqs, callbacks, names);
+ err = vdev->config->find_vqs(vdev, num_vqs, vqs, callbacks, names);
if (err)
- return err;
+ goto out;
virtscsi_init_vq(&vscsi->ctrl_vq, vqs[0]);
virtscsi_init_vq(&vscsi->event_vq, vqs[1]);
- virtscsi_init_vq(&vscsi->req_vq, vqs[2]);
+ for (i = VIRTIO_SCSI_VQ_BASE; i < num_vqs; i++)
+ virtscsi_init_vq(&vscsi->req_vqs[i - VIRTIO_SCSI_VQ_BASE],
+ vqs[i]);
+
+ virtscsi_set_affinity(vscsi, true);
virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);
@@ -631,6 +837,14 @@ static int virtscsi_init(struct virtio_device *vdev,
if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
virtscsi_kick_event_all(vscsi);
+ err = 0;
+
+out:
+ kfree(names);
+ kfree(callbacks);
+ kfree(vqs);
+ if (err)
+ virtscsi_remove_vqs(vdev);
return err;
}
@@ -641,10 +855,21 @@ static int virtscsi_probe(struct virtio_device *vdev)
int err;
u32 sg_elems, num_targets;
u32 cmd_per_lun;
+ u32 num_queues;
+ struct scsi_host_template *hostt;
+
+ /* We need to know how many queues before we allocate. */
+ num_queues = virtscsi_config_get(vdev, num_queues) ? : 1;
num_targets = virtscsi_config_get(vdev, max_target) + 1;
- shost = scsi_host_alloc(&virtscsi_host_template, sizeof(*vscsi));
+ if (num_queues == 1)
+ hostt = &virtscsi_host_template_single;
+ else
+ hostt = &virtscsi_host_template_multi;
+
+ shost = scsi_host_alloc(hostt,
+ sizeof(*vscsi) + sizeof(vscsi->req_vqs[0]) * num_queues);
if (!shost)
return -ENOMEM;
@@ -652,6 +877,7 @@ static int virtscsi_probe(struct virtio_device *vdev)
shost->sg_tablesize = sg_elems;
vscsi = shost_priv(shost);
vscsi->vdev = vdev;
+ vscsi->num_queues = num_queues;
vdev->priv = shost;
err = virtscsi_init(vdev, vscsi);
--
1.8.2.rc2
Wanlong Gao
2013-Mar-23 11:28 UTC
[PATCH V7 5/5] virtio-scsi: reset virtqueue affinity when doing cpu hotplug
Add hot cpu notifier to reset the request virtqueue affinity
when doing cpu hotplug.
Cc: linux-scsi at vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong at cn.fujitsu.com>
Reviewed-by: Asias He <asias at redhat.com>
---
drivers/scsi/virtio_scsi.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 8dcdef0..2168258 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -110,6 +110,9 @@ struct virtio_scsi {
/* If the affinity hint is set for virtqueues */
bool affinity_hint_set;
+ /* CPU hotplug notifier */
+ struct notifier_block nb;
+
struct virtio_scsi_vq ctrl_vq;
struct virtio_scsi_vq event_vq;
struct virtio_scsi_vq req_vqs[];
@@ -762,6 +765,23 @@ static void virtscsi_set_affinity(struct virtio_scsi
*vscsi, bool affinity)
put_online_cpus();
}
+static int virtscsi_cpu_callback(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ struct virtio_scsi *vscsi = container_of(nfb, struct virtio_scsi, nb);
+ switch(action) {
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ __virtscsi_set_affinity(vscsi, true);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
struct virtqueue *vq)
{
@@ -884,6 +904,13 @@ static int virtscsi_probe(struct virtio_device *vdev)
if (err)
goto virtscsi_init_failed;
+ vscsi->nb.notifier_call = &virtscsi_cpu_callback;
+ err = register_hotcpu_notifier(&vscsi->nb);
+ if (err) {
+ pr_err("registering cpu notifier failed\n");
+ goto scsi_add_host_failed;
+ }
+
cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;
@@ -921,6 +948,8 @@ static void virtscsi_remove(struct virtio_device *vdev)
scsi_remove_host(shost);
+ unregister_hotcpu_notifier(&vscsi->nb);
+
virtscsi_remove_vqs(vdev);
scsi_host_put(shost);
}
--
1.8.2.rc2
Bart Van Assche
2013-Mar-25 07:25 UTC
[PATCH V7 4/5] virtio-scsi: introduce multiqueue support
On 03/23/13 12:28, Wanlong Gao wrote:> +static struct virtio_scsi_vq *virtscsi_pick_vq(struct virtio_scsi *vscsi, > + struct virtio_scsi_target_state *tgt) > +{ > + struct virtio_scsi_vq *vq; > + unsigned long flags; > + u32 queue_num; > + > + spin_lock_irqsave(&tgt->tgt_lock, flags); > + > + /* > + * The memory barrier after atomic_inc_return matches > + * the smp_read_barrier_depends() in virtscsi_req_done. > + */ > + if (atomic_inc_return(&tgt->reqs) > 1) > + vq = ACCESS_ONCE(tgt->req_vq); > + else { > + queue_num = smp_processor_id(); > + while (unlikely(queue_num >= vscsi->num_queues)) > + queue_num -= vscsi->num_queues; > + > + tgt->req_vq = vq = &vscsi->req_vqs[queue_num]; > + } > + > + spin_unlock_irqrestore(&tgt->tgt_lock, flags); > + return vq; > +}Is there any reason why the smp_processor_id() % vscsi->num_queues computation in virtscsi_pick_vq() has been implemented as a loop instead of as an arithmetic operation ? If so, I would appreciate it if that could be explained in a comment. Thanks, Bart.
Paolo Bonzini
2013-Mar-25 14:27 UTC
[PATCH V7 4/5] virtio-scsi: introduce multiqueue support
Il 25/03/2013 08:25, Bart Van Assche ha scritto:>> >> + queue_num = smp_processor_id(); >> + while (unlikely(queue_num >= vscsi->num_queues)) >> + queue_num -= vscsi->num_queues; >> + >> + tgt->req_vq = vq = &vscsi->req_vqs[queue_num]; >> + } >> + >> + spin_unlock_irqrestore(&tgt->tgt_lock, flags); >> + return vq; >> +} > > Is there any reason why the smp_processor_id() % vscsi->num_queues > computation in virtscsi_pick_vq() has been implemented as a loop instead > of as an arithmetic operation ? If so, I would appreciate it if that > could be explained in a comment.The expectation is that vscsi->num_queues is the same as the number of CPUs in the virtual machine; see patch 5 too. Paolo
On 03/23/2013 07:28 PM, Wanlong Gao wrote:> This series implements virtio-scsi queue steering, which gives > performance improvements of up to 50% (measured both with QEMU and > tcm_vhost backends). > > This version rebased on Rusty's virtio ring rework patches, which > has already gone into virtio-next today. > We hope this can go into virtio-next together with the virtio ring > rework pathes. > > V7: respin to fix the patch apply error > > V6: rework "redo allocation of target data" (James) > fix comments (Venkatesh) > rebase to virtio-next > > V5: improving the grammar of 1/5 (Paolo) > move the dropping of sg_elems to 'virtio-scsi: use virtqueue_add_sgs for command buffers'. (Asias) > > V4: rebase on virtio ring rework patches (rusty's pending-rebases branch) > > V3 and be found http://marc.info/?l=linux-virtualization&m=136067440717154&w=2 > > > It would probably be easier to get it in via Rusty's tree > because of the prerequisites. James, can we get your Acked-by?James, any thoughts for this version? Thanks, Wanlong Gao> > Paolo Bonzini (3): > virtio-scsi: pass struct virtio_scsi to virtqueue completion function > virtio-scsi: push vq lock/unlock into virtscsi_vq_done > virtio-scsi: introduce multiqueue support > > Wanlong Gao (2): > virtio-scsi: redo allocation of target data > virtio-scsi: reset virtqueue affinity when doing cpu hotplug > > drivers/scsi/virtio_scsi.c | 387 ++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 309 insertions(+), 78 deletions(-) >
On 04/06/2013 04:40 PM, James Bottomley wrote:> On Fri, 2013-04-05 at 16:55 +0800, Wanlong Gao wrote: >> On 03/28/2013 10:22 AM, Wanlong Gao wrote: >>> On 03/23/2013 07:28 PM, Wanlong Gao wrote: >>>> This series implements virtio-scsi queue steering, which gives >>>> performance improvements of up to 50% (measured both with QEMU and >>>> tcm_vhost backends). >>>> >>>> This version rebased on Rusty's virtio ring rework patches, which >>>> has already gone into virtio-next today. >>>> We hope this can go into virtio-next together with the virtio ring >>>> rework pathes. >>>> >>>> V7: respin to fix the patch apply error >>>> >>>> V6: rework "redo allocation of target data" (James) >>>> fix comments (Venkatesh) >>>> rebase to virtio-next >>>> >>>> V5: improving the grammar of 1/5 (Paolo) >>>> move the dropping of sg_elems to 'virtio-scsi: use virtqueue_add_sgs for command buffers'. (Asias) >>>> >>>> V4: rebase on virtio ring rework patches (rusty's pending-rebases branch) >>>> >>>> V3 and be found http://marc.info/?l=linux-virtualization&m=136067440717154&w=2 >>>> >>>> >>>> It would probably be easier to get it in via Rusty's tree >>>> because of the prerequisites. James, can we get your Acked-by? >>> >>> James, any thoughts for this version? >> >> Ping James.... > > Well, I haven't had time to look at anything other than the patch I > commented on. I'm happy with your fix, so you can add my acked by to > that one. Since it's going through the virtio tree, don't wait for me, > put it in and I'll make you fix up anything I find later that I'm > unhappy with.Got it, thank you James. Regards, Wanlong Gao> > James > > >
On Sat, Apr 06, 2013 at 09:40:13AM +0100, James Bottomley wrote:> On Fri, 2013-04-05 at 16:55 +0800, Wanlong Gao wrote: > > On 03/28/2013 10:22 AM, Wanlong Gao wrote: > > > On 03/23/2013 07:28 PM, Wanlong Gao wrote: > > >> This series implements virtio-scsi queue steering, which gives > > >> performance improvements of up to 50% (measured both with QEMU and > > >> tcm_vhost backends). > > >> > > >> This version rebased on Rusty's virtio ring rework patches, which > > >> has already gone into virtio-next today. > > >> We hope this can go into virtio-next together with the virtio ring > > >> rework pathes. > > >> > > >> V7: respin to fix the patch apply error > > >> > > >> V6: rework "redo allocation of target data" (James) > > >> fix comments (Venkatesh) > > >> rebase to virtio-next > > >> > > >> V5: improving the grammar of 1/5 (Paolo) > > >> move the dropping of sg_elems to 'virtio-scsi: use virtqueue_add_sgs for command buffers'. (Asias) > > >> > > >> V4: rebase on virtio ring rework patches (rusty's pending-rebases branch) > > >> > > >> V3 and be found http://marc.info/?l=linux-virtualization&m=136067440717154&w=2 > > >> > > >> > > >> It would probably be easier to get it in via Rusty's tree > > >> because of the prerequisites. James, can we get your Acked-by? > > > > > > James, any thoughts for this version? > > > > Ping James.... > > Well, I haven't had time to look at anything other than the patch I > commented on. I'm happy with your fix, so you can add my acked by to > that one. Since it's going through the virtio tree, don't wait for me, > put it in and I'll make you fix up anything I find later that I'm > unhappy with.So, Rusty, could you pick this up in your virtio-next tree?> James > >-- Asias