From 489471095170ed1c6d0341739a243461638b0e06 Mon Sep 17 00:00:00 2001 From: Mike Marciniszyn Date: Fri, 23 Dec 2011 08:03:41 -0500 Subject: 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 Signed-off-by: Roland Dreier --- drivers/infiniband/hw/qib/qib_verbs.c | 43 +++++++++++++++++++++++++++-------- 1 file changed, 33 insertions(+), 10 deletions(-) (limited to 'drivers/infiniband') diff --git a/drivers/infiniband/hw/qib/qib_verbs.c b/drivers/infiniband/hw/qib/qib_verbs.c index a894762da462..7b6c3bffa9d9 100644 --- a/drivers/infiniband/hw/qib/qib_verbs.c +++ b/drivers/infiniband/hw/qib/qib_verbs.c @@ -913,8 +913,8 @@ static void copy_io(u32 __iomem *piobuf, struct qib_sge_state *ss, __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 @@ static struct qib_verbs_txreq *get_txreq(struct qib_ibdev *dev, 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 @@ static struct qib_verbs_txreq *get_txreq(struct qib_ibdev *dev, 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 @@ static int qib_verbs_send_dma(struct qib_qp *qp, struct qib_ib_header *hdr, 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 @@ unaligned: ibp->n_unaligned++; bail: return ret; +bail_tx: + ret = PTR_ERR(tx); + goto bail; } /* -- cgit v1.2.3