[PATCH 07/23] drbd: improve throttling decisions of background resynchronisation
From: Philipp Reisner
Date: Thu Jul 03 2014 - 04:51:21 EST
From: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
Background resynchronisation does some "side-stepping", or throttles
itself, if it detects application IO activity, and the current resync
rate estimate is above the configured "cmin-rate".
What was not detected: if there is no application IO,
because it blocks on activity log transactions.
Introduce a new atomic_t ap_actlog_cnt, tracking such blocked requests,
and count non-zero as application IO activity.
This counter is exposed at proc_details level 2 and above.
Also make sure to release the currently locked resync extent
if we side-step due to such voluntary throttling.
Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_actlog.c | 29 ++++++++++++++++++++++++++---
drivers/block/drbd/drbd_int.h | 4 +++-
drivers/block/drbd/drbd_main.c | 1 +
drivers/block/drbd/drbd_proc.c | 3 +++
drivers/block/drbd/drbd_receiver.c | 19 ++++++++++++-------
drivers/block/drbd/drbd_req.c | 4 ++++
drivers/block/drbd/drbd_worker.c | 9 ++-------
7 files changed, 51 insertions(+), 18 deletions(-)
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index d7e8066..6ce5c76 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -991,6 +991,15 @@ int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
struct lc_element *e;
struct bm_extent *bm_ext;
int i;
+ bool throttle = drbd_rs_should_slow_down(device, sector, true);
+
+ /* If we need to throttle, a half-locked (only marked BME_NO_WRITES,
+ * not yet BME_LOCKED) extent needs to be kicked out explicitly if we
+ * need to throttle. There is at most one such half-locked extent,
+ * which is remembered in resync_wenr. */
+
+ if (throttle && device->resync_wenr != enr)
+ return -EAGAIN;
spin_lock_irq(&device->al_lock);
if (device->resync_wenr != LC_FREE && device->resync_wenr != enr) {
@@ -1014,8 +1023,10 @@ int drbd_try_rs_begin_io(struct drbd_device *device, sector_t sector)
D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
clear_bit(BME_NO_WRITES, &bm_ext->flags);
device->resync_wenr = LC_FREE;
- if (lc_put(device->resync, &bm_ext->lce) == 0)
+ if (lc_put(device->resync, &bm_ext->lce) == 0) {
+ bm_ext->flags = 0;
device->resync_locked--;
+ }
wake_up(&device->al_wait);
} else {
drbd_alert(device, "LOGIC BUG\n");
@@ -1077,8 +1088,20 @@ proceed:
return 0;
try_again:
- if (bm_ext)
- device->resync_wenr = enr;
+ if (bm_ext) {
+ if (throttle) {
+ D_ASSERT(device, !test_bit(BME_LOCKED, &bm_ext->flags));
+ D_ASSERT(device, test_bit(BME_NO_WRITES, &bm_ext->flags));
+ clear_bit(BME_NO_WRITES, &bm_ext->flags);
+ device->resync_wenr = LC_FREE;
+ if (lc_put(device->resync, &bm_ext->lce) == 0) {
+ bm_ext->flags = 0;
+ device->resync_locked--;
+ }
+ wake_up(&device->al_wait);
+ } else
+ device->resync_wenr = enr;
+ }
spin_unlock_irq(&device->al_lock);
return -EAGAIN;
}
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index fa010ea..81f4af4 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -797,6 +797,7 @@ struct drbd_device {
unsigned int al_writ_cnt;
unsigned int bm_writ_cnt;
atomic_t ap_bio_cnt; /* Requests we need to complete */
+ atomic_t ap_actlog_cnt; /* Requests waiting for activity log */
atomic_t ap_pending_cnt; /* AP data packets on the wire, ack expected */
atomic_t rs_pending_cnt; /* RS request/data packets on the wire */
atomic_t unacked_cnt; /* Need to send replies for */
@@ -1454,7 +1455,8 @@ extern void drbd_endio_write_sec_final(struct drbd_peer_request *peer_req);
extern int drbd_receiver(struct drbd_thread *thi);
extern int drbd_asender(struct drbd_thread *thi);
extern bool drbd_rs_c_min_rate_throttle(struct drbd_device *device);
-extern bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector);
+extern bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector,
+ bool throttle_if_app_is_waiting);
extern int drbd_submit_peer_request(struct drbd_device *,
struct drbd_peer_request *, const unsigned,
const int);
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 5886596..ad7c0e8 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1909,6 +1909,7 @@ void drbd_init_set_defaults(struct drbd_device *device)
drbd_set_defaults(device);
atomic_set(&device->ap_bio_cnt, 0);
+ atomic_set(&device->ap_actlog_cnt, 0);
atomic_set(&device->ap_pending_cnt, 0);
atomic_set(&device->rs_pending_cnt, 0);
atomic_set(&device->unacked_cnt, 0);
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
index 9059d7b..06e6147 100644
--- a/drivers/block/drbd/drbd_proc.c
+++ b/drivers/block/drbd/drbd_proc.c
@@ -335,6 +335,9 @@ static int drbd_seq_show(struct seq_file *seq, void *v)
lc_seq_printf_stats(seq, device->act_log);
put_ldev(device);
}
+
+ if (proc_details >= 2)
+ seq_printf(seq, "\tblocked on activity log: %d\n", atomic_read(&device->ap_actlog_cnt));
}
rcu_read_unlock();
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 7a1078d..0d3cbd8 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2417,13 +2417,14 @@ out_interrupted:
* The current sync rate used here uses only the most recent two step marks,
* to have a short time average so we can react faster.
*/
-bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector)
+bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector,
+ bool throttle_if_app_is_waiting)
{
struct lc_element *tmp;
- bool throttle = true;
+ bool throttle = drbd_rs_c_min_rate_throttle(device);
- if (!drbd_rs_c_min_rate_throttle(device))
- return false;
+ if (!throttle || throttle_if_app_is_waiting)
+ return throttle;
spin_lock_irq(&device->al_lock);
tmp = lc_find(device->resync, BM_SECT_TO_EXT(sector));
@@ -2431,7 +2432,8 @@ bool drbd_rs_should_slow_down(struct drbd_device *device, sector_t sector)
struct bm_extent *bm_ext = lc_entry(tmp, struct bm_extent, lce);
if (test_bit(BME_PRIORITY, &bm_ext->flags))
throttle = false;
- /* Do not slow down if app IO is already waiting for this extent */
+ /* Do not slow down if app IO is already waiting for this extent,
+ * and our progress is necessary for application IO to complete. */
}
spin_unlock_irq(&device->al_lock);
@@ -2456,7 +2458,9 @@ bool drbd_rs_c_min_rate_throttle(struct drbd_device *device)
curr_events = (int)part_stat_read(&disk->part0, sectors[0]) +
(int)part_stat_read(&disk->part0, sectors[1]) -
atomic_read(&device->rs_sect_ev);
- if (!device->rs_last_events || curr_events - device->rs_last_events > 64) {
+
+ if (atomic_read(&device->ap_actlog_cnt)
+ || !device->rs_last_events || curr_events - device->rs_last_events > 64) {
unsigned long rs_left;
int i;
@@ -2646,7 +2650,8 @@ static int receive_DataRequest(struct drbd_connection *connection, struct packet
* we would also throttle its application reads.
* In that case, throttling is done on the SyncTarget only.
*/
- if (device->state.peer != R_PRIMARY && drbd_rs_should_slow_down(device, sector))
+ if (device->state.peer != R_PRIMARY
+ && drbd_rs_should_slow_down(device, sector, false))
schedule_timeout_uninterruptible(HZ/10);
if (drbd_rs_begin_io(device, sector))
goto out_free_e;
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 3f6a6ed..74ebef1 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1218,6 +1218,7 @@ drbd_request_prepare(struct drbd_device *device, struct bio *bio, unsigned long
if (rw == WRITE && req->private_bio && req->i.size
&& !test_bit(AL_SUSPENDED, &device->flags)) {
if (!drbd_al_begin_io_fastpath(device, &req->i)) {
+ atomic_inc(&device->ap_actlog_cnt);
drbd_queue_write(device, req);
return NULL;
}
@@ -1354,6 +1355,7 @@ static void submit_fast_path(struct drbd_device *device, struct list_head *incom
req->rq_state |= RQ_IN_ACT_LOG;
req->in_actlog_jif = jiffies;
+ atomic_dec(&device->ap_actlog_cnt);
}
list_del_init(&req->tl_requests);
@@ -1439,6 +1441,7 @@ skip_fast_path:
list_for_each_entry_safe(req, tmp, &pending, tl_requests) {
req->rq_state |= RQ_IN_ACT_LOG;
req->in_actlog_jif = jiffies;
+ atomic_dec(&device->ap_actlog_cnt);
list_del_init(&req->tl_requests);
drbd_send_and_submit(device, req);
}
@@ -1454,6 +1457,7 @@ skip_fast_path:
if (!was_cold) {
req->rq_state |= RQ_IN_ACT_LOG;
req->in_actlog_jif = jiffies;
+ atomic_dec(&device->ap_actlog_cnt);
/* Corresponding extent was hot after all? */
drbd_send_and_submit(device, req);
} else {
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 0ff8f46..48975a2 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -395,9 +395,6 @@ static int read_for_csum(struct drbd_peer_device *peer_device, sector_t sector,
if (!get_ldev(device))
return -EIO;
- if (drbd_rs_should_slow_down(device, sector))
- goto defer;
-
/* GFP_TRY, because if there is no memory available right now, this may
* be rescheduled for later. It is "only" background resync, after all. */
peer_req = drbd_alloc_peer_req(peer_device, ID_SYNCER /* unused */, sector,
@@ -651,8 +648,7 @@ next_sector:
sector = BM_BIT_TO_SECT(bit);
- if (drbd_rs_should_slow_down(device, sector) ||
- drbd_try_rs_begin_io(device, sector)) {
+ if (drbd_try_rs_begin_io(device, sector)) {
device->bm_resync_fo = bit;
goto requeue;
}
@@ -783,8 +779,7 @@ static int make_ov_request(struct drbd_device *device, int cancel)
size = BM_BLOCK_SIZE;
- if (drbd_rs_should_slow_down(device, sector) ||
- drbd_try_rs_begin_io(device, sector)) {
+ if (drbd_try_rs_begin_io(device, sector)) {
device->ov_position = sector;
goto requeue;
}
--
1.9.1
--
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