drbd: The new, smarter resync speed controller

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_int.h

@@ -928,6 +928,12 @@ enum write_ordering_e {
 	WO_bio_barrier
 };
 
+struct fifo_buffer {
+	int *values;
+	unsigned int head_index;
+	unsigned int size;
+};
+
 struct drbd_conf {
 	/* things that are stored as / read from meta data on disk */
 	unsigned long flags;
@@ -1068,6 +1074,11 @@ struct drbd_conf {
 	u64 ed_uuid; /* UUID of the exposed data */
 	struct mutex state_mutex;
 	char congestion_reason;  /* Why we where congested... */
+	atomic_t rs_sect_in; /* counter to measure the incoming resync data rate */
+	int c_sync_rate; /* current resync rate after delay_probe magic */
+	struct fifo_buffer rs_plan_s; /* correction values of resync planer */
+	int rs_in_flight; /* resync sectors in flight (to proxy, in proxy and from proxy) */
+	int rs_planed;    /* resync sectors already planed */
 };
 
 static inline struct drbd_conf *minor_to_mdev(unsigned int minor)

drivers/block/drbd/drbd_main.c

@@ -2734,6 +2734,7 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	atomic_set(&mdev->net_cnt, 0);
 	atomic_set(&mdev->packet_seq, 0);
 	atomic_set(&mdev->pp_in_use, 0);
+	atomic_set(&mdev->rs_sect_in, 0);
 
 	mutex_init(&mdev->md_io_mutex);
 	mutex_init(&mdev->data.mutex);

drivers/block/drbd/drbd_nl.c

@@ -1587,6 +1587,8 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
 	struct crypto_hash *csums_tfm = NULL;
 	struct syncer_conf sc;
 	cpumask_var_t new_cpu_mask;
+	int *rs_plan_s = NULL;
+	int fifo_size;
 
 	if (!zalloc_cpumask_var(&new_cpu_mask, GFP_KERNEL)) {
 		retcode = ERR_NOMEM;
@@ -1687,6 +1689,16 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
 	if (retcode != NO_ERROR)
 		goto fail;
 
+	fifo_size = (sc.c_plan_ahead * 10 * SLEEP_TIME) / HZ;
+	if (fifo_size != mdev->rs_plan_s.size && fifo_size > 0) {
+		rs_plan_s   = kzalloc(sizeof(int) * fifo_size, GFP_KERNEL);
+		if (!rs_plan_s) {
+			dev_err(DEV, "kmalloc of fifo_buffer failed");
+			retcode = ERR_NOMEM;
+			goto fail;
+		}
+	}
+
 	/* ok, assign the rest of it as well.
 	 * lock against receive_SyncParam() */
 	spin_lock(&mdev->peer_seq_lock);
@@ -1703,6 +1715,15 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
 		mdev->verify_tfm = verify_tfm;
 		verify_tfm = NULL;
 	}
+
+	if (fifo_size != mdev->rs_plan_s.size) {
+		kfree(mdev->rs_plan_s.values);
+		mdev->rs_plan_s.values = rs_plan_s;
+		mdev->rs_plan_s.size   = fifo_size;
+		mdev->rs_planed = 0;
+		rs_plan_s = NULL;
+	}
+
 	spin_unlock(&mdev->peer_seq_lock);
 
 	if (get_ldev(mdev)) {
@@ -1734,6 +1755,7 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n
 
 	kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
 fail:
+	kfree(rs_plan_s);
 	free_cpumask_var(new_cpu_mask);
 	crypto_free_hash(csums_tfm);
 	crypto_free_hash(verify_tfm);

drivers/block/drbd/drbd_receiver.c

@@ -1640,6 +1640,8 @@ static int receive_RSDataReply(struct drbd_conf *mdev, struct p_header *h)
 		drbd_send_ack_dp(mdev, P_NEG_ACK, p);
 	}
 
+	atomic_add(data_size >> 9, &mdev->rs_sect_in);
+
 	return ok;
 }
 
@@ -2810,6 +2812,8 @@ static int receive_SyncParam(struct drbd_conf *mdev, struct p_header *h)
 	struct crypto_hash *verify_tfm = NULL;
 	struct crypto_hash *csums_tfm = NULL;
 	const int apv = mdev->agreed_pro_version;
+	int *rs_plan_s = NULL;
+	int fifo_size = 0;
 
 	exp_max_sz  = apv <= 87 ? sizeof(struct p_rs_param)
 		    : apv == 88 ? sizeof(struct p_rs_param)
@@ -2904,6 +2908,15 @@ static int receive_SyncParam(struct drbd_conf *mdev, struct p_header *h)
 			mdev->sync_conf.c_delay_target = be32_to_cpu(p->c_delay_target);
 			mdev->sync_conf.c_fill_target = be32_to_cpu(p->c_fill_target);
 			mdev->sync_conf.c_max_rate = be32_to_cpu(p->c_max_rate);
+
+			fifo_size = (mdev->sync_conf.c_plan_ahead * 10 * SLEEP_TIME) / HZ;
+			if (fifo_size != mdev->rs_plan_s.size && fifo_size > 0) {
+				rs_plan_s   = kzalloc(sizeof(int) * fifo_size, GFP_KERNEL);
+				if (!rs_plan_s) {
+					dev_err(DEV, "kmalloc of fifo_buffer failed");
+					goto disconnect;
+				}
+			}
 		}
 
 		spin_lock(&mdev->peer_seq_lock);
@@ -2922,6 +2935,12 @@ static int receive_SyncParam(struct drbd_conf *mdev, struct p_header *h)
 			mdev->csums_tfm = csums_tfm;
 			dev_info(DEV, "using csums-alg: \"%s\"\n", p->csums_alg);
 		}
+		if (fifo_size != mdev->rs_plan_s.size) {
+			kfree(mdev->rs_plan_s.values);
+			mdev->rs_plan_s.values = rs_plan_s;
+			mdev->rs_plan_s.size   = fifo_size;
+			mdev->rs_planed = 0;
+		}
 		spin_unlock(&mdev->peer_seq_lock);
 	}
 
@@ -4202,6 +4221,7 @@ static int got_IsInSync(struct drbd_conf *mdev, struct p_header *h)
 	/* rs_same_csums is supposed to count in units of BM_BLOCK_SIZE */
 	mdev->rs_same_csum += (blksize >> BM_BLOCK_SHIFT);
 	dec_rs_pending(mdev);
+	atomic_add(blksize >> 9, &mdev->rs_sect_in);
 
 	return TRUE;
 }

drivers/block/drbd/drbd_worker.c

@@ -422,6 +422,89 @@ void resync_timer_fn(unsigned long data)
 		drbd_queue_work(&mdev->data.work, &mdev->resync_work);
 }
 
+static void fifo_set(struct fifo_buffer *fb, int value)
+{
+	int i;
+
+	for (i = 0; i < fb->size; i++)
+		fb->values[i] += value;
+}
+
+static int fifo_push(struct fifo_buffer *fb, int value)
+{
+	int ov;
+
+	ov = fb->values[fb->head_index];
+	fb->values[fb->head_index++] = value;
+
+	if (fb->head_index >= fb->size)
+		fb->head_index = 0;
+
+	return ov;
+}
+
+static void fifo_add_val(struct fifo_buffer *fb, int value)
+{
+	int i;
+
+	for (i = 0; i < fb->size; i++)
+		fb->values[i] += value;
+}
+
+int drbd_rs_controller(struct drbd_conf *mdev)
+{
+	unsigned int sect_in;  /* Number of sectors that came in since the last turn */
+	unsigned int want;     /* The number of sectors we want in the proxy */
+	int req_sect; /* Number of sectors to request in this turn */
+	int correction; /* Number of sectors more we need in the proxy*/
+	int cps; /* correction per invocation of drbd_rs_controller() */
+	int steps; /* Number of time steps to plan ahead */
+	int curr_corr;
+	int max_sect;
+
+	sect_in = atomic_xchg(&mdev->rs_sect_in, 0); /* Number of sectors that came in */
+	mdev->rs_in_flight -= sect_in;
+
+	spin_lock(&mdev->peer_seq_lock); /* get an atomic view on mdev->rs_plan_s */
+
+	steps = mdev->rs_plan_s.size; /* (mdev->sync_conf.c_plan_ahead * 10 * SLEEP_TIME) / HZ; */
+
+	if (mdev->rs_in_flight + sect_in == 0) { /* At start of resync */
+		want = ((mdev->sync_conf.rate * 2 * SLEEP_TIME) / HZ) * steps;
+	} else { /* normal path */
+		want = mdev->sync_conf.c_fill_target ? mdev->sync_conf.c_fill_target :
+			sect_in * mdev->sync_conf.c_delay_target * HZ / (SLEEP_TIME * 10);
+	}
+
+	correction = want - mdev->rs_in_flight - mdev->rs_planed;
+
+	/* Plan ahead */
+	cps = correction / steps;
+	fifo_add_val(&mdev->rs_plan_s, cps);
+	mdev->rs_planed += cps * steps;
+
+	/* What we do in this step */
+	curr_corr = fifo_push(&mdev->rs_plan_s, 0);
+	spin_unlock(&mdev->peer_seq_lock);
+	mdev->rs_planed -= curr_corr;
+
+	req_sect = sect_in + curr_corr;
+	if (req_sect < 0)
+		req_sect = 0;
+
+	max_sect = (mdev->sync_conf.c_max_rate * 2 * SLEEP_TIME) / HZ;
+	if (req_sect > max_sect)
+		req_sect = max_sect;
+
+	/*
+	dev_warn(DEV, "si=%u if=%d wa=%u co=%d st=%d cps=%d pl=%d cc=%d rs=%d\n",
+		 sect_in, mdev->rs_in_flight, want, correction,
+		 steps, cps, mdev->rs_planed, curr_corr, req_sect);
+	*/
+
+	return req_sect;
+}
+
 int w_make_resync_request(struct drbd_conf *mdev,
 		struct drbd_work *w, int cancel)
 {
@@ -459,7 +542,13 @@ int w_make_resync_request(struct drbd_conf *mdev,
 	max_segment_size = mdev->agreed_pro_version < 94 ?
 		queue_max_segment_size(mdev->rq_queue) : DRBD_MAX_SEGMENT_SIZE;
 
-	number = SLEEP_TIME * mdev->sync_conf.rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
+	if (mdev->rs_plan_s.size) { /* mdev->sync_conf.c_plan_ahead */
+		number = drbd_rs_controller(mdev) >> (BM_BLOCK_SHIFT - 9);
+		mdev->c_sync_rate = number * HZ * (BM_BLOCK_SIZE / 1024) / SLEEP_TIME;
+	} else {
+		mdev->c_sync_rate = mdev->sync_conf.rate;
+		number = SLEEP_TIME * mdev->c_sync_rate  / ((BM_BLOCK_SIZE / 1024) * HZ);
+	}
 	pe = atomic_read(&mdev->rs_pending_cnt);
 
 	mutex_lock(&mdev->data.mutex);
@@ -593,6 +682,7 @@ next_sector:
 	}
 
  requeue:
+	mdev->rs_in_flight += (i << (BM_BLOCK_SHIFT - 9));
 	mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
 	put_ldev(mdev);
 	return 1;
@@ -1419,6 +1509,12 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
 			drbd_resync_finished(mdev);
 		}
 
+		atomic_set(&mdev->rs_sect_in, 0);
+		mdev->rs_in_flight = 0;
+		mdev->rs_planed = 0;
+		spin_lock(&mdev->peer_seq_lock);
+		fifo_set(&mdev->rs_plan_s, 0);
+		spin_unlock(&mdev->peer_seq_lock);
 		/* ns.conn may already be != mdev->state.conn,
 		 * we may have been paused in between, or become paused until
 		 * the timer triggers.