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Message-Id: <200812021631.58810.ossrosch@linux.vnet.ibm.com>
Date: Tue, 2 Dec 2008 16:31:56 +0100
From: Stefan Roscher <ossrosch@...ux.vnet.ibm.com>
To: "LinuxPPC-Dev" <linuxppc-dev@...abs.org>,
"OF-EWG" <ewg@...ts.openfabrics.org>,
LKML <linux-kernel@...r.kernel.org>,
Roland Dreier <rolandd@...co.com>
Cc: raisch@...ibm.com, hnguyen@...ibm.com, fenkes@...ibm.com,
alexschm@...ibm.com, stefan.roscher@...ibm.com
Subject: [PATCH] IB/ehca: replace modulus operations in flush error completion path
With the latest flush error completion patch we introduced modulus operation
to calculate the next index within a qmap. Based on comments from other
mailing lists we decided to optimize this operation by using an addition and
an if-statement instead of modulus, even though this is in error path.
Signed-off-by: Stefan Roscher <stefan.roscher@...ibm.com>
---
drivers/infiniband/hw/ehca/ehca_classes.h | 7 +++++++
drivers/infiniband/hw/ehca/ehca_qp.c | 12 ++++++------
drivers/infiniband/hw/ehca/ehca_reqs.c | 13 ++++++-------
3 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/drivers/infiniband/hw/ehca/ehca_classes.h b/drivers/infiniband/hw/ehca/ehca_classes.h
index 7fc35cf..c825142 100644
--- a/drivers/infiniband/hw/ehca/ehca_classes.h
+++ b/drivers/infiniband/hw/ehca/ehca_classes.h
@@ -175,6 +175,13 @@ struct ehca_queue_map {
unsigned int next_wqe_idx; /* Idx to first wqe to be flushed */
};
+/* function to calculate the next index for the qmap */
+static inline unsigned int next_index(unsigned int cur_index, unsigned int limit)
+{
+ unsigned int temp = cur_index + 1;
+ return (temp == limit) ? 0 : temp;
+}
+
struct ehca_qp {
union {
struct ib_qp ib_qp;
diff --git a/drivers/infiniband/hw/ehca/ehca_qp.c b/drivers/infiniband/hw/ehca/ehca_qp.c
index cadbf0c..f161cf1 100644
--- a/drivers/infiniband/hw/ehca/ehca_qp.c
+++ b/drivers/infiniband/hw/ehca/ehca_qp.c
@@ -1138,14 +1138,14 @@ static int calc_left_cqes(u64 wqe_p, struct ipz_queue *ipz_queue,
return -EFAULT;
}
- tail_idx = (qmap->tail + 1) % qmap->entries;
+ tail_idx = next_index(qmap->tail, qmap->entries);
wqe_idx = q_ofs / ipz_queue->qe_size;
/* check all processed wqes, whether a cqe is requested or not */
while (tail_idx != wqe_idx) {
if (qmap->map[tail_idx].cqe_req)
qmap->left_to_poll++;
- tail_idx = (tail_idx + 1) % qmap->entries;
+ tail_idx = next_index(tail_idx, qmap->entries);
}
/* save index in queue, where we have to start flushing */
qmap->next_wqe_idx = wqe_idx;
@@ -1195,14 +1195,14 @@ static int check_for_left_cqes(struct ehca_qp *my_qp, struct ehca_shca *shca)
} else {
spin_lock_irqsave(&my_qp->send_cq->spinlock, flags);
my_qp->sq_map.left_to_poll = 0;
- my_qp->sq_map.next_wqe_idx = (my_qp->sq_map.tail + 1) %
- my_qp->sq_map.entries;
+ my_qp->sq_map.next_wqe_idx = next_index(my_qp->sq_map.tail,
+ my_qp->sq_map.entries);
spin_unlock_irqrestore(&my_qp->send_cq->spinlock, flags);
spin_lock_irqsave(&my_qp->recv_cq->spinlock, flags);
my_qp->rq_map.left_to_poll = 0;
- my_qp->rq_map.next_wqe_idx = (my_qp->rq_map.tail + 1) %
- my_qp->rq_map.entries;
+ my_qp->rq_map.next_wqe_idx = next_index(my_qp->rq_map.tail,
+ my_qp->rq_map.entries);
spin_unlock_irqrestore(&my_qp->recv_cq->spinlock, flags);
}
diff --git a/drivers/infiniband/hw/ehca/ehca_reqs.c b/drivers/infiniband/hw/ehca/ehca_reqs.c
index 00a648f..c711268 100644
--- a/drivers/infiniband/hw/ehca/ehca_reqs.c
+++ b/drivers/infiniband/hw/ehca/ehca_reqs.c
@@ -726,13 +726,13 @@ repoll:
* set left_to_poll to 0 because in error state, we will not
* get any additional CQEs
*/
- my_qp->sq_map.next_wqe_idx = (my_qp->sq_map.tail + 1) %
- my_qp->sq_map.entries;
+ my_qp->sq_map.next_wqe_idx = next_index(my_qp->sq_map.tail,
+ my_qp->sq_map.entries);
my_qp->sq_map.left_to_poll = 0;
ehca_add_to_err_list(my_qp, 1);
- my_qp->rq_map.next_wqe_idx = (my_qp->rq_map.tail + 1) %
- my_qp->rq_map.entries;
+ my_qp->rq_map.next_wqe_idx = next_index(my_qp->rq_map.tail,
+ my_qp->rq_map.entries);
my_qp->rq_map.left_to_poll = 0;
if (HAS_RQ(my_qp))
ehca_add_to_err_list(my_qp, 0);
@@ -860,9 +860,8 @@ static int generate_flush_cqes(struct ehca_qp *my_qp, struct ib_cq *cq,
/* mark as reported and advance next_wqe pointer */
qmap_entry->reported = 1;
- qmap->next_wqe_idx++;
- if (qmap->next_wqe_idx == qmap->entries)
- qmap->next_wqe_idx = 0;
+ qmap->next_wqe_idx = next_index(qmap->next_wqe_idx,
+ qmap->entries);
qmap_entry = &qmap->map[qmap->next_wqe_idx];
wc++; nr++;
--
1.5.5
--
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