Re: [f2fs-dev] [PATCH RFC v2] mkfs.f2fs: binary decision to calculate SIT/NAT/SSA

Gao Xiang <hsiangkao@xxxxxxx> · Thu, 11 Jan 2018 00:00:54 +0800

Hi Chao,


On 2018/1/10 23:08, Chao Yu wrote:
On 2018/1/10 12:01, Gaoxiang (OS) wrote:
Use binary decision approach to calculate SIT/NAT/SSA segments
it has some benefits when the partition size >= 512G.

                         (bsearch)
psize   main_segments   main_seaments
...
512G    261509          261510
  1 T    523141          523143
  2 T    1046405         1046409
  4 T    2092783         2092791
...

It also clarify that SIT/NAT/SSA are used for main segment area only.

Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
---
Change log from v1:
    - use align_down instead of align_up in get_best_main_zones

  mkfs/f2fs_format.c | 112 ++++++++++++++++++++++++++++++++++++++---------------
  1 file changed, 80 insertions(+), 32 deletions(-)

diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
index a130001..9ca2257 100644
--- a/mkfs/f2fs_format.c
+++ b/mkfs/f2fs_format.c
@@ -145,20 +145,80 @@ static void verify_cur_segs(void)
  		c.cur_seg[i] = next_zone(i - 1);
  }
  
+static u_int32_t get_best_main_zones(void)
+{
+	u_int32_t total_zones = get_sb(segment_count) / (c.segs_per_zone);
+	u_int32_t left = 1, right = total_zones - 1;
+	u_int32_t candicate = 0;
+
+	while (left <= right) {
+		u_int32_t blocks_for_nat;
+		u_int32_t sit_segments, nat_segments, ssa_segments;
+		u_int32_t meta_segments, meta_zones;
+		u_int32_t max_sit_bitmap_size, max_nat_bitmap_size;
+
+		u_int32_t main_zones = (left + right) / 2;
If we start to search zone size from total_zones/2, it can be a little bit
slow, how about starting from the size that calculated by original method,
and then expanding main zone until founding the target?

Thanks,
OK, I will tighten the boundary as much as possible tomorrow.

Thanks,

+		u_int32_t main_segments = c.segs_per_zone * main_zones;
+
+		sit_segments = SEG_ALIGN(SIZE_ALIGN(main_segments,
+			SIT_ENTRY_PER_BLOCK) /* blocks_for_sit */);
+
+		blocks_for_nat = SIZE_ALIGN(main_segments * c.blks_per_seg,
+				NAT_ENTRY_PER_BLOCK);
+
+		max_sit_bitmap_size = min((u_int32_t)MAX_SIT_BITMAP_SIZE,
+			sit_segments * c.blks_per_seg / 8);
+
+		/*
+		 * it's weird because for 1TB storage, payload is still not
+		 * used and max_nat_bitmap_blks is only 21472, which means
+		 * the total number of nodes is 21472 * 409 = 8782048
+		 */
+		if (max_sit_bitmap_size > MAX_SIT_BITMAP_SIZE_IN_CKPT)
+			max_nat_bitmap_size = CHECKSUM_OFFSET -
+					sizeof(struct f2fs_checkpoint) + 1;
+		else
+			max_nat_bitmap_size =
+				CHECKSUM_OFFSET - sizeof(struct f2fs_checkpoint) + 1
+				- max_sit_bitmap_size;
+
+		nat_segments = min(SEG_ALIGN(blocks_for_nat),
+			(max_nat_bitmap_size * 8) / c.blks_per_seg);
+
+		/* each main segment has a ssa block */
+		ssa_segments = SEG_ALIGN(main_segments);
+
+		meta_segments = (get_sb(segment_count_ckpt) +
+			sit_segments * 2 + nat_segments * 2 +
+			ssa_segments);
+
+		meta_zones = ZONE_ALIGN(meta_segments * c.blks_per_seg);
+
+		if (meta_zones + main_zones == total_zones)
+			return main_zones;
+
+		if (meta_zones + main_zones < total_zones) {
+			left = main_zones + 1;
+			candicate = main_zones;
+		} else
+			right = main_zones - 1;
+	}
+
+	return candicate;
+}
+
  static int f2fs_prepare_super_block(void)
  {
  	u_int32_t blk_size_bytes;
  	u_int32_t log_sectorsize, log_sectors_per_block;
  	u_int32_t log_blocksize, log_blks_per_seg;
  	u_int32_t segment_size_bytes, zone_size_bytes;
-	u_int32_t sit_segments;
-	u_int32_t blocks_for_sit, blocks_for_nat, blocks_for_ssa;
-	u_int32_t total_valid_blks_available;
+	u_int32_t blocks_for_sit, blocks_for_nat;
  	u_int64_t zone_align_start_offset, diff;
  	u_int64_t total_meta_zones, total_meta_segments;
  	u_int32_t sit_bitmap_size, max_sit_bitmap_size;
  	u_int32_t max_nat_bitmap_size, max_nat_segments;
-	u_int32_t total_zones;
+	u_int32_t main_zones, main_segments;
  	u_int32_t next_ino;
  	enum quota_type qtype;
  	int i;
@@ -256,22 +316,18 @@ static int f2fs_prepare_super_block(void)
  	set_sb(sit_blkaddr, get_sb(segment0_blkaddr) +
  			get_sb(segment_count_ckpt) * c.blks_per_seg);
  
-	blocks_for_sit = SIZE_ALIGN(get_sb(segment_count), SIT_ENTRY_PER_BLOCK);
+	/* try to do binary decision to get main_zones */
+	main_zones = get_best_main_zones();
+	main_segments = c.segs_per_zone * main_zones;
  
-	sit_segments = SEG_ALIGN(blocks_for_sit);
-
-	set_sb(segment_count_sit, sit_segments * 2);
+	blocks_for_sit = SIZE_ALIGN(main_segments, SIT_ENTRY_PER_BLOCK);
+	set_sb(segment_count_sit, SEG_ALIGN(blocks_for_sit) * 2);
  
  	set_sb(nat_blkaddr, get_sb(sit_blkaddr) + get_sb(segment_count_sit) *
  			c.blks_per_seg);
  
-	total_valid_blks_available = (get_sb(segment_count) -
-			(get_sb(segment_count_ckpt) +
-			get_sb(segment_count_sit))) * c.blks_per_seg;
-
-	blocks_for_nat = SIZE_ALIGN(total_valid_blks_available,
+	blocks_for_nat = SIZE_ALIGN(main_segments * c.blks_per_seg,
  			NAT_ENTRY_PER_BLOCK);
-
  	set_sb(segment_count_nat, SEG_ALIGN(blocks_for_nat));
  	/*
  	 * The number of node segments should not be exceeded a "Threshold".
@@ -312,16 +368,8 @@ static int f2fs_prepare_super_block(void)
  	set_sb(ssa_blkaddr, get_sb(nat_blkaddr) + get_sb(segment_count_nat) *
  			c.blks_per_seg);
  
-	total_valid_blks_available = (get_sb(segment_count) -
-			(get_sb(segment_count_ckpt) +
-			get_sb(segment_count_sit) +
-			get_sb(segment_count_nat))) *
-			c.blks_per_seg;
  
-	blocks_for_ssa = total_valid_blks_available /
-				c.blks_per_seg + 1;
-
-	set_sb(segment_count_ssa, SEG_ALIGN(blocks_for_ssa));
+	set_sb(segment_count_ssa, SEG_ALIGN(main_segments));
  
  	total_meta_segments = get_sb(segment_count_ckpt) +
  		get_sb(segment_count_sit) +
@@ -354,10 +402,7 @@ static int f2fs_prepare_super_block(void)
  		}
  	}
  
-	total_zones = get_sb(segment_count) / (c.segs_per_zone) -
-							total_meta_zones;
-
-	set_sb(section_count, total_zones * c.secs_per_zone);
+	set_sb(section_count, main_zones * c.secs_per_zone);
  
  	set_sb(segment_count_main, get_sb(section_count) * c.segs_per_sec);
  
@@ -373,6 +418,9 @@ static int f2fs_prepare_super_block(void)
  		return -1;
  	}
  
+	ASSERT((total_meta_zones + main_zones) * c.segs_per_zone
+		== get_sb(segment_count));
+
  	c.reserved_segments =
  			(2 * (100 / c.overprovision + 1) + 6)
  			* c.segs_per_sec;
@@ -404,15 +452,15 @@ static int f2fs_prepare_super_block(void)
  					qtype, next_ino - 1);
  	}
  
-	if (total_zones <= 6) {
+	if (main_zones <= 6) {
  		MSG(1, "\tError: %d zones: Need more zones "
-			"by shrinking zone size\n", total_zones);
+			"by shrinking zone size\n", main_zones);
  		return -1;
  	}
  
  	if (c.heap) {
  		c.cur_seg[CURSEG_HOT_NODE] =
-				last_section(last_zone(total_zones));
+				last_section(last_zone(main_zones));
  		c.cur_seg[CURSEG_WARM_NODE] = prev_zone(CURSEG_HOT_NODE);
  		c.cur_seg[CURSEG_COLD_NODE] = prev_zone(CURSEG_WARM_NODE);
  		c.cur_seg[CURSEG_HOT_DATA] = prev_zone(CURSEG_COLD_NODE);
@@ -424,10 +472,10 @@ static int f2fs_prepare_super_block(void)
  		c.cur_seg[CURSEG_COLD_NODE] = next_zone(CURSEG_WARM_NODE);
  		c.cur_seg[CURSEG_HOT_DATA] = next_zone(CURSEG_COLD_NODE);
  		c.cur_seg[CURSEG_COLD_DATA] =
-				max(last_zone((total_zones >> 2)),
+				max(last_zone((main_zones >> 2)),
  					next_zone(CURSEG_COLD_NODE));
  		c.cur_seg[CURSEG_WARM_DATA] =
-				max(last_zone((total_zones >> 1)),
+				max(last_zone((main_zones >> 1)),
  					next_zone(CURSEG_COLD_DATA));
  	}
  








