forked from Minki/linux
dm cache: add io_tracker
A little class that keeps track of the volume of io that is in flight, and the length of time that a device has been idle for. FIXME: rather than jiffes, may be best to use ktime_t (to support faster devices). Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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@ -25,6 +25,79 @@ DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle,
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/*----------------------------------------------------------------*/
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#define IOT_RESOLUTION 4
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struct io_tracker {
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spinlock_t lock;
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/*
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* Sectors of in-flight IO.
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*/
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sector_t in_flight;
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/*
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* The time, in jiffies, when this device became idle (if it is
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* indeed idle).
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*/
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unsigned long idle_time;
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unsigned long last_update_time;
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};
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static void iot_init(struct io_tracker *iot)
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{
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spin_lock_init(&iot->lock);
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iot->in_flight = 0ul;
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iot->idle_time = 0ul;
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iot->last_update_time = jiffies;
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}
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static bool __iot_idle_for(struct io_tracker *iot, unsigned long jifs)
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{
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if (iot->in_flight)
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return false;
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return time_after(jiffies, iot->idle_time + jifs);
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}
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static bool iot_idle_for(struct io_tracker *iot, unsigned long jifs)
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{
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bool r;
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unsigned long flags;
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spin_lock_irqsave(&iot->lock, flags);
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r = __iot_idle_for(iot, jifs);
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spin_unlock_irqrestore(&iot->lock, flags);
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return r;
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}
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static void iot_io_begin(struct io_tracker *iot, sector_t len)
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{
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unsigned long flags;
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spin_lock_irqsave(&iot->lock, flags);
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iot->in_flight += len;
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spin_unlock_irqrestore(&iot->lock, flags);
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}
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static void __iot_io_end(struct io_tracker *iot, sector_t len)
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{
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iot->in_flight -= len;
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if (!iot->in_flight)
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iot->idle_time = jiffies;
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}
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static void iot_io_end(struct io_tracker *iot, sector_t len)
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{
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unsigned long flags;
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spin_lock_irqsave(&iot->lock, flags);
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__iot_io_end(iot, len);
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spin_unlock_irqrestore(&iot->lock, flags);
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}
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/*----------------------------------------------------------------*/
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/*
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* Glossary:
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*
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