lightnvm: pblk: sched. metadata on write thread

At the moment, line metadata is persisted on a separate work queue, that
is kicked each time that a line is closed. The assumption when designing
this was that freeing the write thread from creating a new write request
was better than the potential impact of writes colliding on the media
(user I/O and metadata I/O). Experimentation has proven that this
assumption is wrong; collision can cause up to 25% of bandwidth and
introduce long tail latencies on the write thread, which potentially
cause user write threads to spend more time spinning to get a free entry
on the write buffer.

This patch moves the metadata logic to the write thread. When a line is
closed, remaining metadata is written in memory and is placed on a
metadata queue. The write thread then takes the metadata corresponding
to the previous line, creates the write request and schedules it to
minimize collisions on the media. Using this approach, we see that we
can saturate the media's bandwidth, which helps reducing both write
latencies and the spinning time for user writer threads.

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 35 insertions, 32 deletions

diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
index 84671b44bddb..ba02d0bc3e45 100644
--- a/drivers/lightnvm/pblk-recovery.c
+++ b/drivers/lightnvm/pblk-recovery.c
@@ -120,18 +120,18 @@ int pblk_recov_setup_rq(struct pblk *pblk, struct pblk_c_ctx *c_ctx,
 	return 0;
 }
 
-__le64 *pblk_recov_get_lba_list(struct pblk *pblk, struct line_emeta *emeta)
+__le64 *pblk_recov_get_lba_list(struct pblk *pblk, struct line_emeta *emeta_buf)
 {
 	u32 crc;
 
-	crc = pblk_calc_emeta_crc(pblk, emeta);
-	if (le32_to_cpu(emeta->crc) != crc)
+	crc = pblk_calc_emeta_crc(pblk, emeta_buf);
+	if (le32_to_cpu(emeta_buf->crc) != crc)
 		return NULL;
 
-	if (le32_to_cpu(emeta->header.identifier) != PBLK_MAGIC)
+	if (le32_to_cpu(emeta_buf->header.identifier) != PBLK_MAGIC)
 		return NULL;
 
-	return pblk_line_emeta_to_lbas(emeta);
+	return emeta_to_lbas(pblk, emeta_buf);
 }
 
 static int pblk_recov_l2p_from_emeta(struct pblk *pblk, struct pblk_line *line)
@@ -139,19 +139,20 @@ static int pblk_recov_l2p_from_emeta(struct pblk *pblk, struct pblk_line *line)
 	struct nvm_tgt_dev *dev = pblk->dev;
 	struct nvm_geo *geo = &dev->geo;
 	struct pblk_line_meta *lm = &pblk->lm;
-	struct line_emeta *emeta = line->emeta;
+	struct pblk_emeta *emeta = line->emeta;
+	struct line_emeta *emeta_buf = emeta->buf;
 	__le64 *lba_list;
 	int data_start;
 	int nr_data_lbas, nr_valid_lbas, nr_lbas = 0;
 	int i;
 
-	lba_list = pblk_recov_get_lba_list(pblk, emeta);
+	lba_list = pblk_recov_get_lba_list(pblk, emeta_buf);
 	if (!lba_list)
 		return 1;
 
 	data_start = pblk_line_smeta_start(pblk, line) + lm->smeta_sec;
-	nr_data_lbas = lm->sec_per_line - lm->emeta_sec;
-	nr_valid_lbas = le64_to_cpu(emeta->nr_valid_lbas);
+	nr_data_lbas = lm->sec_per_line - lm->emeta_sec[0];
+	nr_valid_lbas = le64_to_cpu(emeta_buf->nr_valid_lbas);
 
 	for (i = data_start; i < nr_data_lbas && nr_lbas < nr_valid_lbas; i++) {
 		struct ppa_addr ppa;
@@ -169,7 +170,7 @@ static int pblk_recov_l2p_from_emeta(struct pblk *pblk, struct pblk_line *line)
 			if (test_and_set_bit(i, line->invalid_bitmap))
 				WARN_ONCE(1, "pblk: rec. double invalidate:\n");
 			else
-				line->vsc--;
+				le32_add_cpu(line->vsc, -1);
 			spin_unlock(&line->lock);
 
 			continue;
@@ -181,7 +182,7 @@ static int pblk_recov_l2p_from_emeta(struct pblk *pblk, struct pblk_line *line)
 
 	if (nr_valid_lbas != nr_lbas)
 		pr_err("pblk: line %d - inconsistent lba list(%llu/%d)\n",
-				line->id, line->emeta->nr_valid_lbas, nr_lbas);
+				line->id, emeta_buf->nr_valid_lbas, nr_lbas);
 
 	line->left_msecs = 0;
 
@@ -195,7 +196,7 @@ static int pblk_calc_sec_in_line(struct pblk *pblk, struct pblk_line *line)
 	struct pblk_line_meta *lm = &pblk->lm;
 	int nr_bb = bitmap_weight(line->blk_bitmap, lm->blk_per_line);
 
-	return lm->sec_per_line - lm->smeta_sec - lm->emeta_sec -
+	return lm->sec_per_line - lm->smeta_sec - lm->emeta_sec[0] -
 				nr_bb * geo->sec_per_blk;
 }
 
@@ -333,7 +334,7 @@ static int pblk_recov_pad_oob(struct pblk *pblk, struct pblk_line *line,
 	struct bio *bio;
 	void *data;
 	dma_addr_t dma_ppa_list, dma_meta_list;
-	__le64 *lba_list = pblk_line_emeta_to_lbas(line->emeta);
+	__le64 *lba_list = emeta_to_lbas(pblk, line->emeta->buf);
 	u64 w_ptr = line->cur_sec;
 	int left_line_ppas = line->left_msecs;
 	int rq_ppas, rq_len;
@@ -770,8 +771,9 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 	struct pblk_line_meta *lm = &pblk->lm;
 	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 	struct pblk_line *line, *tline, *data_line = NULL;
-	struct line_smeta *smeta;
-	struct line_emeta *emeta;
+	struct pblk_smeta *smeta;
+	struct pblk_emeta *emeta;
+	struct line_smeta *smeta_buf;
 	int found_lines = 0, recovered_lines = 0, open_lines = 0;
 	int is_next = 0;
 	int meta_line;
@@ -784,8 +786,9 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 	spin_lock(&l_mg->free_lock);
 	meta_line = find_first_zero_bit(&l_mg->meta_bitmap, PBLK_DATA_LINES);
 	set_bit(meta_line, &l_mg->meta_bitmap);
-	smeta = l_mg->sline_meta[meta_line].meta;
-	emeta = l_mg->eline_meta[meta_line].meta;
+	smeta = l_mg->sline_meta[meta_line];
+	emeta = l_mg->eline_meta[meta_line];
+	smeta_buf = smeta->buf;
 	spin_unlock(&l_mg->free_lock);
 
 	/* Order data lines using their sequence number */
@@ -796,33 +799,33 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 
 		memset(smeta, 0, lm->smeta_len);
 		line->smeta = smeta;
-		line->lun_bitmap = ((void *)(smeta)) +
+		line->lun_bitmap = ((void *)(smeta_buf)) +
 						sizeof(struct line_smeta);
 
 		/* Lines that cannot be read are assumed as not written here */
 		if (pblk_line_read_smeta(pblk, line))
 			continue;
 
-		crc = pblk_calc_smeta_crc(pblk, smeta);
-		if (le32_to_cpu(smeta->crc) != crc)
+		crc = pblk_calc_smeta_crc(pblk, smeta_buf);
+		if (le32_to_cpu(smeta_buf->crc) != crc)
 			continue;
 
-		if (le32_to_cpu(smeta->header.identifier) != PBLK_MAGIC)
+		if (le32_to_cpu(smeta_buf->header.identifier) != PBLK_MAGIC)
 			continue;
 
-		if (le16_to_cpu(smeta->header.version) != 1) {
+		if (le16_to_cpu(smeta_buf->header.version) != 1) {
 			pr_err("pblk: found incompatible line version %u\n",
-					smeta->header.version);
+					smeta_buf->header.version);
 			return ERR_PTR(-EINVAL);
 		}
 
 		/* The first valid instance uuid is used for initialization */
 		if (!valid_uuid) {
-			memcpy(pblk->instance_uuid, smeta->header.uuid, 16);
+			memcpy(pblk->instance_uuid, smeta_buf->header.uuid, 16);
 			valid_uuid = 1;
 		}
 
-		if (memcmp(pblk->instance_uuid, smeta->header.uuid, 16)) {
+		if (memcmp(pblk->instance_uuid, smeta_buf->header.uuid, 16)) {
 			pr_debug("pblk: ignore line %u due to uuid mismatch\n",
 					i);
 			continue;
@@ -830,9 +833,9 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 
 		/* Update line metadata */
 		spin_lock(&line->lock);
-		line->id = le32_to_cpu(line->smeta->header.id);
-		line->type = le16_to_cpu(line->smeta->header.type);
-		line->seq_nr = le64_to_cpu(line->smeta->seq_nr);
+		line->id = le32_to_cpu(smeta_buf->header.id);
+		line->type = le16_to_cpu(smeta_buf->header.type);
+		line->seq_nr = le64_to_cpu(smeta_buf->seq_nr);
 		spin_unlock(&line->lock);
 
 		/* Update general metadata */
@@ -848,7 +851,7 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 		pblk_recov_line_add_ordered(&recov_list, line);
 		found_lines++;
 		pr_debug("pblk: recovering data line %d, seq:%llu\n",
-						line->id, smeta->seq_nr);
+						line->id, smeta_buf->seq_nr);
 	}
 
 	if (!found_lines) {
@@ -868,15 +871,15 @@ struct pblk_line *pblk_recov_l2p(struct pblk *pblk)
 
 		recovered_lines++;
 		/* Calculate where emeta starts based on the line bb */
-		off = lm->sec_per_line - lm->emeta_sec;
+		off = lm->sec_per_line - lm->emeta_sec[0];
 		nr_bb = bitmap_weight(line->blk_bitmap, lm->blk_per_line);
 		off -= nr_bb * geo->sec_per_pl;
 
-		memset(emeta, 0, lm->emeta_len);
+		memset(&emeta->buf, 0, lm->emeta_len[0]);
 		line->emeta = emeta;
 		line->emeta_ssec = off;
 
-		if (pblk_line_read_emeta(pblk, line)) {
+		if (pblk_line_read_emeta(pblk, line, line->emeta->buf)) {
 			pblk_recov_l2p_from_oob(pblk, line);
 			goto next;
 		}