lib/ftl: improved padding during shutdown

Padding requests are issued in multiple batches at the same time
when shutdown occurs. This allows for faster removal.

Change-Id: Iea40d2418bedbd7cf3c6865e5eb8f85871db13cd
Signed-off-by: Kozlowski Mateusz <mateusz.kozlowski@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/454578
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Wojciech Malikowski <wojciech.malikowski@intel.com>
Reviewed-by: Konrad Sztyber <konrad.sztyber@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

lib/ftl/ftl_band.c

@@ -120,7 +120,7 @@ ftl_tail_md_num_lbks(const struct spdk_ftl_dev *dev)
 }
 
 static uint64_t
-ftl_band_tail_md_offset(struct ftl_band *band)
+ftl_band_tail_md_offset(const struct ftl_band *band)
 {
 	return ftl_band_num_usable_lbks(band) -
 	       ftl_tail_md_num_lbks(band->dev);
@@ -515,6 +515,22 @@ ftl_band_num_usable_lbks(const struct ftl_band *band)
 	return band->num_chunks * ftl_dev_lbks_in_chunk(band->dev);
 }
 
+size_t
+ftl_band_user_lbks_left(const struct ftl_band *band, size_t offset)
+{
+	size_t tail_md_offset = ftl_band_tail_md_offset(band);
+
+	if (spdk_unlikely(offset <= ftl_head_md_num_lbks(band->dev))) {
+		return ftl_band_user_lbks(band);
+	}
+
+	if (spdk_unlikely(offset > tail_md_offset)) {
+		return 0;
+	}
+
+	return tail_md_offset - offset;
+}
+
 size_t
 ftl_band_user_lbks(const struct ftl_band *band)
 {

lib/ftl/ftl_band.h

@@ -172,6 +172,7 @@ struct ftl_ppa ftl_band_next_xfer_ppa(struct ftl_band *band, struct ftl_ppa ppa,
 struct ftl_ppa ftl_band_next_ppa(struct ftl_band *band, struct ftl_ppa ppa,
 				 size_t offset);
 size_t		ftl_band_num_usable_lbks(const struct ftl_band *band);
+size_t		ftl_band_user_lbks_left(const struct ftl_band *band, size_t offset);
 size_t		ftl_band_user_lbks(const struct ftl_band *band);
 void		ftl_band_set_addr(struct ftl_band *band, uint64_t lba,
 				  struct ftl_ppa ppa);

lib/ftl/ftl_core.c

@@ -470,6 +470,12 @@ ftl_wptr_advance(struct ftl_wptr *wptr, size_t xfer_size)
 	}
 }
 
+static size_t
+ftl_wptr_user_lbks_left(const struct ftl_wptr *wptr)
+{
+	return ftl_band_user_lbks_left(wptr->band, wptr->offset);
+}
+
 static int
 ftl_wptr_ready(struct ftl_wptr *wptr)
 {
@@ -605,11 +611,13 @@ ftl_remove_free_bands(struct spdk_ftl_dev *dev)
 }
 
 static void
-ftl_process_shutdown(struct spdk_ftl_dev *dev)
+ftl_wptr_process_shutdown(struct ftl_wptr *wptr)
 {
+	struct spdk_ftl_dev *dev = wptr->dev;
 	size_t size = ftl_rwb_num_acquired(dev->rwb, FTL_RWB_TYPE_INTERNAL) +
 		      ftl_rwb_num_acquired(dev->rwb, FTL_RWB_TYPE_USER);
 	size_t num_active = dev->xfer_size * ftl_rwb_get_active_batches(dev->rwb);
+	size_t band_length, rwb_free_space, pad_length;
 
 	num_active = num_active ? num_active : dev->xfer_size;
 	if (size >= num_active) {
@@ -622,10 +630,12 @@ ftl_process_shutdown(struct spdk_ftl_dev *dev)
 		ftl_remove_free_bands(dev);
 	}
 
+	band_length = ftl_wptr_user_lbks_left(wptr);
+	rwb_free_space = ftl_rwb_size(dev->rwb) - size;
+	pad_length = spdk_min(band_length, rwb_free_space);
+
 	/* Pad write buffer until band is full */
-	/* TODO : It would be better to request padding to as many as PUs possible */
-	/* instead of requesting to one PU at a time */
-	ftl_rwb_pad(dev, num_active - size);
+	ftl_rwb_pad(dev, pad_length);
 }
 
 static int
@@ -1314,7 +1324,7 @@ ftl_wptr_process_writes(struct ftl_wptr *wptr)
 	}
 
 	if (dev->halt) {
-		ftl_process_shutdown(dev);
+		ftl_wptr_process_shutdown(wptr);
 	}
 
 	batch = ftl_rwb_pop(dev->rwb);

lib/ftl/ftl_rwb.c

@@ -324,6 +324,12 @@ ftl_rwb_num_batches(const struct ftl_rwb *rwb)
 	return rwb->num_batches;
 }
 
+size_t
+ftl_rwb_size(const struct ftl_rwb *rwb)
+{
+	return rwb->num_batches * rwb->xfer_size;
+}
+
 size_t
 ftl_rwb_batch_get_offset(const struct ftl_rwb_batch *batch)
 {

lib/ftl/ftl_rwb.h

@@ -101,6 +101,7 @@ void	ftl_rwb_set_limits(struct ftl_rwb *rwb, const size_t limit[FTL_RWB_TYPE_MAX
 void	ftl_rwb_get_limits(struct ftl_rwb *rwb, size_t limit[FTL_RWB_TYPE_MAX]);
 size_t	ftl_rwb_num_acquired(struct ftl_rwb *rwb, enum ftl_rwb_entry_type type);
 size_t	ftl_rwb_num_batches(const struct ftl_rwb *rwb);
+size_t	ftl_rwb_size(const struct ftl_rwb *rwb);
 struct ftl_rwb_entry *ftl_rwb_acquire(struct ftl_rwb *rwb, enum ftl_rwb_entry_type type);
 struct ftl_rwb_batch *ftl_rwb_pop(struct ftl_rwb *rwb);
 struct ftl_rwb_batch *ftl_rwb_first_batch(struct ftl_rwb *rwb);