IB/qib: Optimize CQ callbacks

The current workqueue implemention has the following performance
deficiencies on QDR HCAs:

- The CQ call backs tend to run on the CPUs processing the
  receive queues
- The single thread queue isn't optimal for multiple HCAs

This patch adds a dedicated per HCA bound thread to process CQ callbacks.

Reviewed-by: Ramkrishna Vepa <ramkrishna.vepa@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

4 files changed, 76 insertions, 24 deletions

diff --git a/drivers/infiniband/hw/qib/qib.h b/drivers/infiniband/hw/qib/qib.h
index 2ee82e6550c7..3a78b92cbd4e 100644
--- a/drivers/infiniband/hw/qib/qib.h
+++ b/drivers/infiniband/hw/qib/qib.h
@@ -1,7 +1,7 @@
 #ifndef _QIB_KERNEL_H
 #define _QIB_KERNEL_H
 /*
- * Copyright (c) 2012 Intel Corporation.  All rights reserved.
+ * Copyright (c) 2012, 2013 Intel Corporation.  All rights reserved.
  * Copyright (c) 2006 - 2012 QLogic Corporation. All rights reserved.
  * Copyright (c) 2003, 2004, 2005, 2006 PathScale, Inc. All rights reserved.
  *
@@ -51,6 +51,7 @@
 #include <linux/completion.h>
 #include <linux/kref.h>
 #include <linux/sched.h>
+#include <linux/kthread.h>
 
 #include "qib_common.h"
 #include "qib_verbs.h"
@@ -1090,6 +1091,8 @@ struct qib_devdata {
         u16 psxmitwait_check_rate;
         /* high volume overflow errors defered to tasklet */
         struct tasklet_struct error_tasklet;
+        /* per device cq worker */
+        struct kthread_worker *worker;
 
         int assigned_node_id; /* NUMA node closest to HCA */
 };
diff --git a/drivers/infiniband/hw/qib/qib_cq.c b/drivers/infiniband/hw/qib/qib_cq.c
index 5246aa486bbe..ab4e11cfab15 100644
--- a/drivers/infiniband/hw/qib/qib_cq.c
+++ b/drivers/infiniband/hw/qib/qib_cq.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2013 Intel Corporation.  All rights reserved.
  * Copyright (c) 2006, 2007, 2008, 2010 QLogic Corporation. All rights reserved.
  * Copyright (c) 2005, 2006 PathScale, Inc. All rights reserved.
  *
@@ -34,8 +35,10 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/kthread.h>
 
 #include "qib_verbs.h"
+#include "qib.h"
 
 /**
  * qib_cq_enter - add a new entry to the completion queue
@@ -102,13 +105,18 @@ void qib_cq_enter(struct qib_cq *cq, struct ib_wc *entry, int solicited)
         if (cq->notify == IB_CQ_NEXT_COMP ||
             (cq->notify == IB_CQ_SOLICITED &&
              (solicited || entry->status != IB_WC_SUCCESS))) {
-                cq->notify = IB_CQ_NONE;
-                cq->triggered++;
+                struct kthread_worker *worker;
                 /*
                  * This will cause send_complete() to be called in
                  * another thread.
                  */
-                queue_work(qib_cq_wq, &cq->comptask);
+                smp_rmb();
+                worker = cq->dd->worker;
+                if (likely(worker)) {
+                        cq->notify = IB_CQ_NONE;
+                        cq->triggered++;
+                        queue_kthread_work(worker, &cq->comptask);
+                }
         }
 
         spin_unlock_irqrestore(&cq->lock, flags);
@@ -163,7 +171,7 @@ bail:
         return npolled;
 }
 
-static void send_complete(struct work_struct *work)
+static void send_complete(struct kthread_work *work)
 {
         struct qib_cq *cq = container_of(work, struct qib_cq, comptask);
 
@@ -287,11 +295,12 @@ struct ib_cq *qib_create_cq(struct ib_device *ibdev, int entries,
          * The number of entries should be >= the number requested or return
          * an error.
          */
+        cq->dd = dd_from_dev(dev);
         cq->ibcq.cqe = entries;
         cq->notify = IB_CQ_NONE;
         cq->triggered = 0;
         spin_lock_init(&cq->lock);
-        INIT_WORK(&cq->comptask, send_complete);
+        init_kthread_work(&cq->comptask, send_complete);
         wc->head = 0;
         wc->tail = 0;
         cq->queue = wc;
@@ -323,7 +332,7 @@ int qib_destroy_cq(struct ib_cq *ibcq)
         struct qib_ibdev *dev = to_idev(ibcq->device);
         struct qib_cq *cq = to_icq(ibcq);
 
-        flush_work(&cq->comptask);
+        flush_kthread_work(&cq->comptask);
         spin_lock(&dev->n_cqs_lock);
         dev->n_cqs_allocated--;
         spin_unlock(&dev->n_cqs_lock);
@@ -483,3 +492,49 @@ bail_free:
 bail:
         return ret;
 }
+
+int qib_cq_init(struct qib_devdata *dd)
+{
+        int ret = 0;
+        int cpu;
+        struct task_struct *task;
+
+        if (dd->worker)
+                return 0;
+        dd->worker = kzalloc(sizeof(*dd->worker), GFP_KERNEL);
+        if (!dd->worker)
+                return -ENOMEM;
+        init_kthread_worker(dd->worker);
+        task = kthread_create_on_node(
+                kthread_worker_fn,
+                dd->worker,
+                dd->assigned_node_id,
+                "qib_cq%d", dd->unit);
+        if (IS_ERR(task))
+                goto task_fail;
+        cpu = cpumask_first(cpumask_of_node(dd->assigned_node_id));
+        kthread_bind(task, cpu);
+        wake_up_process(task);
+out:
+        return ret;
+task_fail:
+        ret = PTR_ERR(task);
+        kfree(dd->worker);
+        dd->worker = NULL;
+        goto out;
+}
+
+void qib_cq_exit(struct qib_devdata *dd)
+{
+        struct kthread_worker *worker;
+
+        worker = dd->worker;
+        if (!worker)
+                return;
+        /* blocks future queuing from send_complete() */
+        dd->worker = NULL;
+        smp_wmb();
+        flush_kthread_worker(worker);
+        kthread_stop(worker->task);
+        kfree(worker);
+}
diff --git a/drivers/infiniband/hw/qib/qib_init.c b/drivers/infiniband/hw/qib/qib_init.c
index e02217b5c46d..ff36903474ea 100644
--- a/drivers/infiniband/hw/qib/qib_init.c
+++ b/drivers/infiniband/hw/qib/qib_init.c
@@ -97,8 +97,6 @@ unsigned qib_wc_pat = 1; /* default (1) is to use PAT, not MTRR */
 module_param_named(wc_pat, qib_wc_pat, uint, S_IRUGO);
 MODULE_PARM_DESC(wc_pat, "enable write-combining via PAT mechanism");
 
-struct workqueue_struct *qib_cq_wq;
-
 static void verify_interrupt(unsigned long);
 
 static struct idr qib_unit_table;
@@ -445,6 +443,7 @@ static int loadtime_init(struct qib_devdata *dd)
         dd->intrchk_timer.function = verify_interrupt;
         dd->intrchk_timer.data = (unsigned long) dd;
 
+        ret = qib_cq_init(dd);
 done:
         return ret;
 }
@@ -1215,12 +1214,6 @@ static int __init qlogic_ib_init(void)
         if (ret)
                 goto bail;
 
-        qib_cq_wq = create_singlethread_workqueue("qib_cq");
-        if (!qib_cq_wq) {
-                ret = -ENOMEM;
-                goto bail_dev;
-        }
-
         /*
          * These must be called before the driver is registered with
          * the PCI subsystem.
@@ -1233,7 +1226,7 @@ static int __init qlogic_ib_init(void)
         ret = pci_register_driver(&qib_driver);
         if (ret < 0) {
                 pr_err("Unable to register driver: error %d\n", -ret);
-                goto bail_unit;
+                goto bail_dev;
         }
 
         /* not fatal if it doesn't work */
@@ -1241,13 +1234,11 @@ static int __init qlogic_ib_init(void)
                 pr_err("Unable to register ipathfs\n");
         goto bail; /* all OK */
 
-bail_unit:
+bail_dev:
 #ifdef CONFIG_INFINIBAND_QIB_DCA
         dca_unregister_notify(&dca_notifier);
 #endif
         idr_destroy(&qib_unit_table);
-        destroy_workqueue(qib_cq_wq);
-bail_dev:
         qib_dev_cleanup();
 bail:
         return ret;
@@ -1273,8 +1264,6 @@ static void __exit qlogic_ib_cleanup(void)
 #endif
         pci_unregister_driver(&qib_driver);
 
-        destroy_workqueue(qib_cq_wq);
-
         qib_cpulist_count = 0;
         kfree(qib_cpulist);
 
@@ -1365,6 +1354,7 @@ static void cleanup_device_data(struct qib_devdata *dd)
         }
         kfree(tmp);
         kfree(dd->boardname);
+        qib_cq_exit(dd);
 }
 
 /*
diff --git a/drivers/infiniband/hw/qib/qib_verbs.h b/drivers/infiniband/hw/qib/qib_verbs.h
index aff8b2c17886..86c2cb3c9caf 100644
--- a/drivers/infiniband/hw/qib/qib_verbs.h
+++ b/drivers/infiniband/hw/qib/qib_verbs.h
@@ -41,6 +41,7 @@
 #include <linux/interrupt.h>
 #include <linux/kref.h>
 #include <linux/workqueue.h>
+#include <linux/kthread.h>
 #include <linux/completion.h>
 #include <rdma/ib_pack.h>
 #include <rdma/ib_user_verbs.h>
@@ -267,7 +268,8 @@ struct qib_cq_wc {
  */
 struct qib_cq {
         struct ib_cq ibcq;
-        struct work_struct comptask;
+        struct kthread_work comptask;
+        struct qib_devdata *dd;
         spinlock_t lock; /* protect changes in this struct */
         u8 notify;
         u8 triggered;
@@ -832,8 +834,6 @@ static inline int qib_send_ok(struct qib_qp *qp)
                  !(qp->s_flags & QIB_S_ANY_WAIT_SEND));
 }
 
-extern struct workqueue_struct *qib_cq_wq;
-
 /*
  * This must be called with s_lock held.
  */
@@ -972,6 +972,10 @@ int qib_query_srq(struct ib_srq *ibsrq, struct ib_srq_attr *attr);
 
 int qib_destroy_srq(struct ib_srq *ibsrq);
 
+int qib_cq_init(struct qib_devdata *dd);
+
+void qib_cq_exit(struct qib_devdata *dd);
+
 void qib_cq_enter(struct qib_cq *cq, struct ib_wc *entry, int sig);
 
 int qib_poll_cq(struct ib_cq *ibcq, int num_entries, struct ib_wc *entry);