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[SCSI] zfcp: optimize zfcp_qdio_account

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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>
This commit is contained in:
Heiko Carstens 2009-08-18 15:43:32 +02:00 committed by James Bottomley
parent b592e89ac9
commit 41e05a12c7
2 changed files with 6 additions and 7 deletions
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2
drivers/s390/scsi/zfcp_def.h
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@ -438,7 +438,7 @@ struct zfcp_qdio {
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;

11
drivers/s390/scsi/zfcp_qdio.c
View file

@ -56,16 +56,15 @@ static void zfcp_qdio_zero_sbals(struct qdio_buffer *sbal[], int first, int cnt)
}
/* 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;