[SCSI] zfcp: optimize zfcp_qdio_account
Remove expensive ktime_get()/ktime_us_delta() functions from the hot
path and use get_clock_monotonic() instead. This elimates seven
function calls and avoids a lot of unnecessary calculations.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index cc98eea..7da2fad 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/drivers/s390/scsi/zfcp_def.h
@@ -438,7 +438,7 @@
struct zfcp_qdio_queue req_q;
spinlock_t stat_lock;
spinlock_t req_q_lock;
- ktime_t req_q_time;
+ unsigned long long req_q_time;
u64 req_q_util;
atomic_t req_q_full;
wait_queue_head_t req_q_wq;
diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c
index 2b499e2..6c5228b 100644
--- a/drivers/s390/scsi/zfcp_qdio.c
+++ b/drivers/s390/scsi/zfcp_qdio.c
@@ -56,16 +56,15 @@
}
/* this needs to be called prior to updating the queue fill level */
-static void zfcp_qdio_account(struct zfcp_qdio *qdio)
+static inline void zfcp_qdio_account(struct zfcp_qdio *qdio)
{
- ktime_t now;
- s64 span;
+ unsigned long long now, span;
int free, used;
spin_lock(&qdio->stat_lock);
- now = ktime_get();
- span = ktime_us_delta(now, qdio->req_q_time);
- free = max(0, atomic_read(&qdio->req_q.count));
+ now = get_clock_monotonic();
+ span = (now - qdio->req_q_time) >> 12;
+ free = atomic_read(&qdio->req_q.count);
used = QDIO_MAX_BUFFERS_PER_Q - free;
qdio->req_q_util += used * span;
qdio->req_q_time = now;