>-Original Message-
>From: Chao Yu [mailto:yuch...@huawei.com]
>Sent: Friday, April 20, 2018 9:53 AM
>To: jaeg...@kernel.org
>Cc: linux-kernel@vger.kernel.org; linux-f2fs-de...@lists.sourceforge.net
>Subject: [f2fs-dev] [PATCH] f2fs: sepearte hot/cold in free nid
>
>As most indirect node, dindirect node, and xattr node won't be updated
>after they are created, but inode node and other direct node will change
>more frequently, so store their nat entries mixedly in whole nat table
>will suffer:
>- fragment nat table soon due to different update rate
>- more nat block update due to fragmented nat table
>
BTW, should we enable this patch: f2fs: reuse nids more aggressively?
I think it will decrease nat area fragment and will decrease io of nat?
>In order to solve above issue, we're trying to separate whole nat table to
>two part:
>a. Hot free nid area:
> - range: [nid #0, nid #x)
> - store node block address for
> * inode node
> * other direct node
>b. Cold free nid area:
> - range: [nid #x, max nid)
> - store node block address for
> * indirect node
> * dindirect node
> * xattr node
>
>Allocation strategy example:
>
>Free nid: '-'
>Used nid: '='
>
>1. Initial status:
>Free Nids:
>|---|
> ^ ^ ^
> ^
>Alloc Range: |---|
>|---|
> hot_start hot_end
> cold_start cold_end
>
>2. Free nids have ran out:
>Free Nids:
>|===-===|
> ^ ^ ^
> ^
>Alloc Range: |===|
>|===|
> hot_start hot_end
> cold_start cold_end
>
>3. Expand hot/cold area range:
>Free Nids:
>|===-===|
> ^ ^ ^
> ^
>Alloc Range: |===|
>|===|
> hot_start hot_end cold_start
> cold_end
>
>4. Hot free nids have ran out:
>Free Nids:
>|===-===|
> ^ ^ ^
> ^
>Alloc Range: |===|
>|===|
> hot_start hot_end cold_start
> cold_end
>
>5. Expand hot area range, hot/cold area boundary has been fixed:
>Free Nids:
>|===-===|
> ^ ^
> ^
>Alloc Range:
>|===|===|
> hot_start hot_end(cold_start)
> cold_end
>
>Run xfstests with generic/*:
>
>before
>node_write:169660
>cp_count: 60118
>node/cp2.82
>
>after:
>node_write:159145
>cp_count: 84501
>node/cp: 2.64
>
>Signed-off-by: Chao Yu
>---
> fs/f2fs/checkpoint.c | 4 -
> fs/f2fs/debug.c | 6 +-
> fs/f2fs/f2fs.h | 19 +++-
> fs/f2fs/inode.c | 2 +-
> fs/f2fs/namei.c | 2 +-
> fs/f2fs/node.c | 302 ---
> fs/f2fs/node.h | 17 +--
> fs/f2fs/segment.c| 8 +-
> fs/f2fs/shrinker.c | 3 +-
> fs/f2fs/xattr.c | 10 +-
> 10 files changed, 221 insertions(+), 152 deletions(-)
>
>diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>index 96785ffc6181..c17feec72c74 100644
>--- a/fs/f2fs/checkpoint.c
>+++ b/fs/f2fs/checkpoint.c
>@@ -1029,14 +1029,10 @@ int f2fs_sync_inode_meta(struct f2fs_sb_info *sbi)
> static void __prepare_cp_block(struct f2fs_sb_info *sbi)
> {
> struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
>- struct f2fs_nm_info *nm_i = NM_I(sbi);
>- nid_t last_nid = nm_i->next_scan_nid;
>
>- next_free_nid(sbi, &last_nid);
> ckpt->valid_block_count = cpu_to_le64(valid_user_blocks(sbi));
> ckpt->valid_node_count = cpu_to_le32(valid_node_count(sbi));
> ckpt->valid_inode_count = cpu_to_
