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block: Seperate read and write statistics of in_flight requests v2

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Commit a9327cac44 added seperate read
and write statistics of in_flight requests. And exported the number
of read and write requests in progress seperately through sysfs.

But  Corrado Zoccolo <[email protected]> reported getting strange
output from "iostat -kx 2". Global values for service time and
utilization were garbage. For interval values, utilization was always
100%, and service time is higher than normal.

So this was reverted by commit 0f78ab9899

The problem was in part_round_stats_single(), I missed the following:
        if (now == part->stamp)
                return;

-       if (part->in_flight) {
+       if (part_in_flight(part)) {
                __part_stat_add(cpu, part, time_in_queue,
                                part_in_flight(part) * (now - part->stamp));
                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));

With this chunk included, the reported regression gets fixed.

Signed-off-by: Nikanth Karthikesan <[email protected]>

--
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Nikanth Karthikesan 2009-10-06 20:16:55 +02:00 • committed by Jens Axboe
commit 316d315bff
6 changed files with 43 additions and 20 deletions
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16
drivers/md/dm.c
View file

@ -130,7 +130,7 @@ struct mapped_device {
/*
* A list of ios that arrived while we were suspended.
*/
atomic_t pending;
atomic_t pending[2];
wait_queue_head_t wait;
struct work_struct work;
struct bio_list deferred;
@ -453,13 +453,14 @@ static void start_io_acct(struct dm_io *io)
{
struct mapped_device *md = io->md;
int cpu;
int rw = bio_data_dir(io->bio);
io->start_time = jiffies;
cpu = part_stat_lock();
part_round_stats(cpu, &dm_disk(md)->part0);
part_stat_unlock();
dm_disk(md)->part0.in_flight = atomic_inc_return(&md->pending);
dm_disk(md)->part0.in_flight[rw] = atomic_inc_return(&md->pending[rw]);
}
static void end_io_acct(struct dm_io *io)
@ -479,8 +480,9 @@ static void end_io_acct(struct dm_io *io)
* After this is decremented the bio must not be touched if it is
* a barrier.
*/
dm_disk(md)->part0.in_flight = pending =
atomic_dec_return(&md->pending);
dm_disk(md)->part0.in_flight[rw] = pending =
atomic_dec_return(&md->pending[rw]);
pending += atomic_read(&md->pending[rw^0x1]);
/* nudge anyone waiting on suspend queue */
if (!pending)
@ -1785,7 +1787,8 @@ static struct mapped_device *alloc_dev(int minor)
if (!md->disk)
goto bad_disk;
atomic_set(&md->pending, 0);
atomic_set(&md->pending[0], 0);
atomic_set(&md->pending[1], 0);
init_waitqueue_head(&md->wait);
INIT_WORK(&md->work, dm_wq_work);
init_waitqueue_head(&md->eventq);
@ -2088,7 +2091,8 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
break;
}
spin_unlock_irqrestore(q->queue_lock, flags);
} else if (!atomic_read(&md->pending))
} else if (!atomic_read(&md->pending[0]) &&
!atomic_read(&md->pending[1]))
break;
if (interruptible == TASK_INTERRUPTIBLE &&