dm: add statistics support
Support the collection of I/O statistics on user-defined regions of
a DM device. If no regions are defined no statistics are collected so
there isn't any performance impact. Only bio-based DM devices are
currently supported.
Each user-defined region specifies a starting sector, length and step.
Individual statistics will be collected for each step-sized area within
the range specified.
The I/O statistics counters for each step-sized area of a region are
in the same format as /sys/block/*/stat or /proc/diskstats but extra
counters (12 and 13) are provided: total time spent reading and
writing in milliseconds. All these counters may be accessed by sending
the @stats_print message to the appropriate DM device via dmsetup.
The creation of DM statistics will allocate memory via kmalloc or
fallback to using vmalloc space. At most, 1/4 of the overall system
memory may be allocated by DM statistics. The admin can see how much
memory is used by reading
/sys/module/dm_mod/parameters/stats_current_allocated_bytes
See Documentation/device-mapper/statistics.txt for more details.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7faeaa3..6a5e9ed 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -60,6 +60,7 @@
struct bio *bio;
unsigned long start_time;
spinlock_t endio_lock;
+ struct dm_stats_aux stats_aux;
};
/*
@@ -198,6 +199,8 @@
/* zero-length flush that will be cloned and submitted to targets */
struct bio flush_bio;
+
+ struct dm_stats stats;
};
/*
@@ -269,6 +272,7 @@
dm_io_init,
dm_kcopyd_init,
dm_interface_init,
+ dm_statistics_init,
};
static void (*_exits[])(void) = {
@@ -279,6 +283,7 @@
dm_io_exit,
dm_kcopyd_exit,
dm_interface_exit,
+ dm_statistics_exit,
};
static int __init dm_init(void)
@@ -384,6 +389,16 @@
return r;
}
+sector_t dm_get_size(struct mapped_device *md)
+{
+ return get_capacity(md->disk);
+}
+
+struct dm_stats *dm_get_stats(struct mapped_device *md)
+{
+ return &md->stats;
+}
+
static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
struct mapped_device *md = bdev->bd_disk->private_data;
@@ -466,8 +481,9 @@
static void start_io_acct(struct dm_io *io)
{
struct mapped_device *md = io->md;
+ struct bio *bio = io->bio;
int cpu;
- int rw = bio_data_dir(io->bio);
+ int rw = bio_data_dir(bio);
io->start_time = jiffies;
@@ -476,6 +492,10 @@
part_stat_unlock();
atomic_set(&dm_disk(md)->part0.in_flight[rw],
atomic_inc_return(&md->pending[rw]));
+
+ if (unlikely(dm_stats_used(&md->stats)))
+ dm_stats_account_io(&md->stats, bio->bi_rw, bio->bi_sector,
+ bio_sectors(bio), false, 0, &io->stats_aux);
}
static void end_io_acct(struct dm_io *io)
@@ -491,6 +511,10 @@
part_stat_add(cpu, &dm_disk(md)->part0, ticks[rw], duration);
part_stat_unlock();
+ if (unlikely(dm_stats_used(&md->stats)))
+ dm_stats_account_io(&md->stats, bio->bi_rw, bio->bi_sector,
+ bio_sectors(bio), true, duration, &io->stats_aux);
+
/*
* After this is decremented the bio must not be touched if it is
* a flush.
@@ -1519,7 +1543,7 @@
return;
}
-static int dm_request_based(struct mapped_device *md)
+int dm_request_based(struct mapped_device *md)
{
return blk_queue_stackable(md->queue);
}
@@ -1958,6 +1982,8 @@
md->flush_bio.bi_bdev = md->bdev;
md->flush_bio.bi_rw = WRITE_FLUSH;
+ dm_stats_init(&md->stats);
+
/* Populate the mapping, nobody knows we exist yet */
spin_lock(&_minor_lock);
old_md = idr_replace(&_minor_idr, md, minor);
@@ -2009,6 +2035,7 @@
put_disk(md->disk);
blk_cleanup_queue(md->queue);
+ dm_stats_cleanup(&md->stats);
module_put(THIS_MODULE);
kfree(md);
}
@@ -2150,7 +2177,7 @@
/*
* Wipe any geometry if the size of the table changed.
*/
- if (size != get_capacity(md->disk))
+ if (size != dm_get_size(md))
memset(&md->geometry, 0, sizeof(md->geometry));
__set_size(md, size);
@@ -2696,6 +2723,38 @@
return r;
}
+/*
+ * Internal suspend/resume works like userspace-driven suspend. It waits
+ * until all bios finish and prevents issuing new bios to the target drivers.
+ * It may be used only from the kernel.
+ *
+ * Internal suspend holds md->suspend_lock, which prevents interaction with
+ * userspace-driven suspend.
+ */
+
+void dm_internal_suspend(struct mapped_device *md)
+{
+ mutex_lock(&md->suspend_lock);
+ if (dm_suspended_md(md))
+ return;
+
+ set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
+ synchronize_srcu(&md->io_barrier);
+ flush_workqueue(md->wq);
+ dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
+}
+
+void dm_internal_resume(struct mapped_device *md)
+{
+ if (dm_suspended_md(md))
+ goto done;
+
+ dm_queue_flush(md);
+
+done:
+ mutex_unlock(&md->suspend_lock);
+}
+
/*-----------------------------------------------------------------
* Event notification.
*---------------------------------------------------------------*/
