IB/srp: Split send and recieve CQs to reduce number of interrupts

We can reduce the number of IB interrupts from two interrupts per
srp_queuecommand() call to one by using separate CQs for send and
receive completions and processing send completions by polling every
time a TX IU is allocated.

Receive completion events still trigger an interrupt.

Signed-off-by: Bart Van Assche <bart.vanassche@gmail.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 53 insertions, 25 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 54c8fe25c423..441ea7c2e7c4 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -80,7 +80,8 @@ MODULE_PARM_DESC(mellanox_workarounds,
 
 static void srp_add_one(struct ib_device *device);
 static void srp_remove_one(struct ib_device *device);
-static void srp_completion(struct ib_cq *cq, void *target_ptr);
+static void srp_recv_completion(struct ib_cq *cq, void *target_ptr);
+static void srp_send_completion(struct ib_cq *cq, void *target_ptr);
 static int srp_cm_handler(struct ib_cm_id *cm_id, struct ib_cm_event *event);
 
 static struct scsi_transport_template *ib_srp_transport_template;
@@ -227,14 +228,22 @@ static int srp_create_target_ib(struct srp_target_port *target)
         if (!init_attr)
                 return -ENOMEM;
 
-        target->cq = ib_create_cq(target->srp_host->srp_dev->dev,
-                                  srp_completion, NULL, target, SRP_CQ_SIZE, 0);
-        if (IS_ERR(target->cq)) {
-                ret = PTR_ERR(target->cq);
+        target->recv_cq = ib_create_cq(target->srp_host->srp_dev->dev,
+                                       srp_recv_completion, NULL, target, SRP_RQ_SIZE, 0);
+        if (IS_ERR(target->recv_cq)) {
+                ret = PTR_ERR(target->recv_cq);
                 goto out;
         }
 
-        ib_req_notify_cq(target->cq, IB_CQ_NEXT_COMP);
+        target->send_cq = ib_create_cq(target->srp_host->srp_dev->dev,
+                                       srp_send_completion, NULL, target, SRP_SQ_SIZE, 0);
+        if (IS_ERR(target->send_cq)) {
+                ret = PTR_ERR(target->send_cq);
+                ib_destroy_cq(target->recv_cq);
+                goto out;
+        }
+
+        ib_req_notify_cq(target->recv_cq, IB_CQ_NEXT_COMP);
 
         init_attr->event_handler       = srp_qp_event;
         init_attr->cap.max_send_wr     = SRP_SQ_SIZE;
@@ -243,20 +252,22 @@ static int srp_create_target_ib(struct srp_target_port *target)
         init_attr->cap.max_send_sge    = 1;
         init_attr->sq_sig_type         = IB_SIGNAL_ALL_WR;
         init_attr->qp_type             = IB_QPT_RC;
-        init_attr->send_cq             = target->cq;
-        init_attr->recv_cq             = target->cq;
+        init_attr->send_cq             = target->send_cq;
+        init_attr->recv_cq             = target->recv_cq;
 
         target->qp = ib_create_qp(target->srp_host->srp_dev->pd, init_attr);
         if (IS_ERR(target->qp)) {
                 ret = PTR_ERR(target->qp);
-                ib_destroy_cq(target->cq);
+                ib_destroy_cq(target->send_cq);
+                ib_destroy_cq(target->recv_cq);
                 goto out;
         }
 
         ret = srp_init_qp(target, target->qp);
         if (ret) {
                 ib_destroy_qp(target->qp);
-                ib_destroy_cq(target->cq);
+                ib_destroy_cq(target->send_cq);
+                ib_destroy_cq(target->recv_cq);
                 goto out;
         }
 
@@ -270,7 +281,8 @@ static void srp_free_target_ib(struct srp_target_port *target)
         int i;
 
         ib_destroy_qp(target->qp);
-        ib_destroy_cq(target->cq);
+        ib_destroy_cq(target->send_cq);
+        ib_destroy_cq(target->recv_cq);
 
         for (i = 0; i < SRP_RQ_SIZE; ++i)
                 srp_free_iu(target->srp_host, target->rx_ring[i]);
@@ -568,7 +580,9 @@ static int srp_reconnect_target(struct srp_target_port *target)
         if (ret)
                 goto err;
 
-        while (ib_poll_cq(target->cq, 1, &wc) > 0)
+        while (ib_poll_cq(target->recv_cq, 1, &wc) > 0)
+                ; /* nothing */
+        while (ib_poll_cq(target->send_cq, 1, &wc) > 0)
                 ; /* nothing */
 
         spin_lock_irq(target->scsi_host->host_lock);
@@ -851,7 +865,7 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
         struct srp_iu *iu;
         u8 opcode;
 
-        iu = target->rx_ring[wc->wr_id & ~SRP_OP_RECV];
+        iu = target->rx_ring[wc->wr_id];
 
         dev = target->srp_host->srp_dev->dev;
         ib_dma_sync_single_for_cpu(dev, iu->dma, target->max_ti_iu_len,
@@ -898,7 +912,7 @@ static void srp_handle_recv(struct srp_target_port *target, struct ib_wc *wc)
                                       DMA_FROM_DEVICE);
 }
 
-static void srp_completion(struct ib_cq *cq, void *target_ptr)
+static void srp_recv_completion(struct ib_cq *cq, void *target_ptr)
 {
         struct srp_target_port *target = target_ptr;
         struct ib_wc wc;
@@ -907,17 +921,31 @@ static void srp_completion(struct ib_cq *cq, void *target_ptr)
         while (ib_poll_cq(cq, 1, &wc) > 0) {
                 if (wc.status) {
                         shost_printk(KERN_ERR, target->scsi_host,
-                                     PFX "failed %s status %d\n",
-                                     wc.wr_id & SRP_OP_RECV ? "receive" : "send",
+                                     PFX "failed receive status %d\n",
                                      wc.status);
                         target->qp_in_error = 1;
                         break;
                 }
 
-                if (wc.wr_id & SRP_OP_RECV)
-                        srp_handle_recv(target, &wc);
-                else
-                        ++target->tx_tail;
+                srp_handle_recv(target, &wc);
+        }
+}
+
+static void srp_send_completion(struct ib_cq *cq, void *target_ptr)
+{
+        struct srp_target_port *target = target_ptr;
+        struct ib_wc wc;
+
+        while (ib_poll_cq(cq, 1, &wc) > 0) {
+                if (wc.status) {
+                        shost_printk(KERN_ERR, target->scsi_host,
+                                     PFX "failed send status %d\n",
+                                     wc.status);
+                        target->qp_in_error = 1;
+                        break;
+                }
+
+                ++target->tx_tail;
         }
 }
 
@@ -930,7 +958,7 @@ static int __srp_post_recv(struct srp_target_port *target)
         int ret;
 
         next     = target->rx_head & (SRP_RQ_SIZE - 1);
-        wr.wr_id = next | SRP_OP_RECV;
+        wr.wr_id = next;
         iu       = target->rx_ring[next];
 
         list.addr   = iu->dma;
@@ -970,6 +998,8 @@ static struct srp_iu *__srp_get_tx_iu(struct srp_target_port *target,
 {
         s32 min = (req_type == SRP_REQ_TASK_MGMT) ? 1 : 2;
 
+        srp_send_completion(target->send_cq, target);
+
         if (target->tx_head - target->tx_tail >= SRP_SQ_SIZE)
                 return NULL;
 
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index e185b907fc12..5a80eac6fdaa 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -60,7 +60,6 @@ enum {
         SRP_RQ_SHIFT            = 6,
         SRP_RQ_SIZE             = 1 << SRP_RQ_SHIFT,
         SRP_SQ_SIZE             = SRP_RQ_SIZE - 1,
-        SRP_CQ_SIZE             = SRP_SQ_SIZE + SRP_RQ_SIZE,
 
         SRP_TAG_TSK_MGMT        = 1 << (SRP_RQ_SHIFT + 1),
 
@@ -69,8 +68,6 @@ enum {
         SRP_FMR_DIRTY_SIZE      = SRP_FMR_POOL_SIZE / 4
 };
 
-#define SRP_OP_RECV             (1 << 31)
-
 enum srp_target_state {
         SRP_TARGET_LIVE,
         SRP_TARGET_CONNECTING,
@@ -133,7 +130,8 @@ struct srp_target_port {
         int                     path_query_id;
 
         struct ib_cm_id        *cm_id;
-        struct ib_cq           *cq;
+        struct ib_cq           *recv_cq;
+        struct ib_cq           *send_cq;
         struct ib_qp           *qp;
 
         int                     max_ti_iu_len;