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| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2009-08-18 15:43:32 +0200 |
|---|---|---|
| committer | James Bottomley <James.Bottomley@suse.de> | 2009-09-05 08:49:49 -0500 |
| commit | 41e05a12c7aae16f0381103af3e5ca791e87ce59 (patch) | |
| tree | 3db57f11d9f2183215a52796fea113ce96b5abd8 /drivers/s390 | |
| parent | b592e89ac9af521be164490e45c53c93e89c776f (diff) | |
| download | lwn-41e05a12c7aae16f0381103af3e5ca791e87ce59.tar.gz lwn-41e05a12c7aae16f0381103af3e5ca791e87ce59.zip | |
[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>
Diffstat (limited to 'drivers/s390')
| -rw-r--r-- | drivers/s390/scsi/zfcp_def.h | 2 | ||||
| -rw-r--r-- | drivers/s390/scsi/zfcp_qdio.c | 11 |
2 files changed, 6 insertions, 7 deletions
diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h index cc98eead2c3c..7da2fad8f515 100644 --- a/drivers/s390/scsi/zfcp_def.h +++ b/drivers/s390/scsi/zfcp_def.h @@ -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; diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c index 2b499e28ff1f..6c5228b627fc 100644 --- a/drivers/s390/scsi/zfcp_qdio.c +++ b/drivers/s390/scsi/zfcp_qdio.c @@ -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; |