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[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>
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2 changed files with 6 additions and 7 deletions
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@ -438,7 +438,7 @@ struct zfcp_qdio {
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struct zfcp_qdio_queue req_q;
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spinlock_t stat_lock;
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spinlock_t req_q_lock;
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ktime_t req_q_time;
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unsigned long long req_q_time;
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u64 req_q_util;
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atomic_t req_q_full;
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wait_queue_head_t req_q_wq;
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@ -56,16 +56,15 @@ static void zfcp_qdio_zero_sbals(struct qdio_buffer *sbal[], int first, int cnt)
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}
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/* this needs to be called prior to updating the queue fill level */
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static void zfcp_qdio_account(struct zfcp_qdio *qdio)
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static inline void zfcp_qdio_account(struct zfcp_qdio *qdio)
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{
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ktime_t now;
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s64 span;
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unsigned long long now, span;
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int free, used;
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spin_lock(&qdio->stat_lock);
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now = ktime_get();
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span = ktime_us_delta(now, qdio->req_q_time);
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free = max(0, atomic_read(&qdio->req_q.count));
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now = get_clock_monotonic();
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span = (now - qdio->req_q_time) >> 12;
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free = atomic_read(&qdio->req_q.count);
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used = QDIO_MAX_BUFFERS_PER_Q - free;
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qdio->req_q_util += used * span;
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qdio->req_q_time = now;
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