IB/qib: Optimize locking for get_txreq()
The current code locks the QP s_lock, followed by the pending_lock, I
guess to to protect against the allocate failing.
This patch only locks the pending_lock, assuming that the empty case
is an exeception, in which case the pending_lock is dropped, and the
original code is executed. This will save a lock of s_lock in the
normal case.
The observation is that the sdma descriptors will deplete at twice the
rate of txreq's, so this should be rare.
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@qlogic.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/hw/qib/qib_verbs.c b/drivers/infiniband/hw/qib/qib_verbs.c
index a894762..7b6c3bf 100644
--- a/drivers/infiniband/hw/qib/qib_verbs.c
+++ b/drivers/infiniband/hw/qib/qib_verbs.c
@@ -913,8 +913,8 @@
__raw_writel(last, piobuf);
}
-static struct qib_verbs_txreq *get_txreq(struct qib_ibdev *dev,
- struct qib_qp *qp, int *retp)
+static noinline struct qib_verbs_txreq *__get_txreq(struct qib_ibdev *dev,
+ struct qib_qp *qp)
{
struct qib_verbs_txreq *tx;
unsigned long flags;
@@ -926,8 +926,9 @@
struct list_head *l = dev->txreq_free.next;
list_del(l);
+ spin_unlock(&dev->pending_lock);
+ spin_unlock_irqrestore(&qp->s_lock, flags);
tx = list_entry(l, struct qib_verbs_txreq, txreq.list);
- *retp = 0;
} else {
if (ib_qib_state_ops[qp->state] & QIB_PROCESS_RECV_OK &&
list_empty(&qp->iowait)) {
@@ -935,14 +936,33 @@
qp->s_flags |= QIB_S_WAIT_TX;
list_add_tail(&qp->iowait, &dev->txwait);
}
- tx = NULL;
qp->s_flags &= ~QIB_S_BUSY;
- *retp = -EBUSY;
+ spin_unlock(&dev->pending_lock);
+ spin_unlock_irqrestore(&qp->s_lock, flags);
+ tx = ERR_PTR(-EBUSY);
}
+ return tx;
+}
- spin_unlock(&dev->pending_lock);
- spin_unlock_irqrestore(&qp->s_lock, flags);
+static inline struct qib_verbs_txreq *get_txreq(struct qib_ibdev *dev,
+ struct qib_qp *qp)
+{
+ struct qib_verbs_txreq *tx;
+ unsigned long flags;
+ spin_lock_irqsave(&dev->pending_lock, flags);
+ /* assume the list non empty */
+ if (likely(!list_empty(&dev->txreq_free))) {
+ struct list_head *l = dev->txreq_free.next;
+
+ list_del(l);
+ spin_unlock_irqrestore(&dev->pending_lock, flags);
+ tx = list_entry(l, struct qib_verbs_txreq, txreq.list);
+ } else {
+ /* call slow path to get the extra lock */
+ spin_unlock_irqrestore(&dev->pending_lock, flags);
+ tx = __get_txreq(dev, qp);
+ }
return tx;
}
@@ -1122,9 +1142,9 @@
goto bail;
}
- tx = get_txreq(dev, qp, &ret);
- if (!tx)
- goto bail;
+ tx = get_txreq(dev, qp);
+ if (IS_ERR(tx))
+ goto bail_tx;
control = dd->f_setpbc_control(ppd, plen, qp->s_srate,
be16_to_cpu(hdr->lrh[0]) >> 12);
@@ -1195,6 +1215,9 @@
ibp->n_unaligned++;
bail:
return ret;
+bail_tx:
+ ret = PTR_ERR(tx);
+ goto bail;
}
/*