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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>
This commit is contained in:
Joe Thornber 2015-05-15 13:45:30 +01:00 committed by Mike Snitzer
parent fb4100ae7f
commit 77289d3207
1 changed files with 73 additions and 0 deletions
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73
drivers/md/dm-cache-target.c
View File

@ -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:
*