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Commit 77289d32 authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
Browse files

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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent fb4100ae

drivers/md/dm-cache-target.c

+73 −0
Original line number Diff line number Diff line
@@ -25,6 +25,79 @@ DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(cache_copy_throttle, 


/*----------------------------------------------------------------*/



#define IOT_RESOLUTION 4



struct io_tracker {

	spinlock_t lock;



	/*

	 * Sectors of in-flight IO.

	 */

	sector_t in_flight;



	/*

	 * The time, in jiffies, when this device became idle (if it is

	 * indeed idle).

	 */

	unsigned long idle_time;

	unsigned long last_update_time;

};



static void iot_init(struct io_tracker *iot)

{

	spin_lock_init(&iot->lock);

	iot->in_flight = 0ul;

	iot->idle_time = 0ul;

	iot->last_update_time = jiffies;

}



static bool __iot_idle_for(struct io_tracker *iot, unsigned long jifs)

{

	if (iot->in_flight)

		return false;



	return time_after(jiffies, iot->idle_time + jifs);

}



static bool iot_idle_for(struct io_tracker *iot, unsigned long jifs)

{

	bool r;

	unsigned long flags;



	spin_lock_irqsave(&iot->lock, flags);

	r = __iot_idle_for(iot, jifs);

	spin_unlock_irqrestore(&iot->lock, flags);



	return r;

}



static void iot_io_begin(struct io_tracker *iot, sector_t len)

{

	unsigned long flags;



	spin_lock_irqsave(&iot->lock, flags);

	iot->in_flight += len;

	spin_unlock_irqrestore(&iot->lock, flags);

}



static void __iot_io_end(struct io_tracker *iot, sector_t len)

{

	iot->in_flight -= len;

	if (!iot->in_flight)

		iot->idle_time = jiffies;

}



static void iot_io_end(struct io_tracker *iot, sector_t len)

{

	unsigned long flags;



	spin_lock_irqsave(&iot->lock, flags);

	__iot_io_end(iot, len);

	spin_unlock_irqrestore(&iot->lock, flags);

}



/*----------------------------------------------------------------*/



/*

 * Glossary:

 *