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Date: Wed, 1 Mar 2017 11:35:45 -0800
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <yuchao0@...wei.com>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH V2] f2fs: introduce free nid bitmap
Hi Chao,
BTW, we need to add a shrinker for this as well, right?
Thanks,
On 02/23, Chao Yu wrote:
> In scenario of intensively node allocation, free nids will be ran out
> soon, then it needs to stop to load free nids by traversing NAT blocks,
> in worse case, if NAT blocks does not be cached in memory, it generates
> IOs which slows down our foreground operations.
>
> In order to speed up node allocation, in this patch we introduce a new
> free_nid_bitmap array, so there is an bitmap table for each NAT block,
> Once the NAT block is loaded, related bitmap cache will be switched on,
> and bitmap will be set during traversing nat entries in NAT block, later
> we can query and update nid usage status in memory completely.
>
> With such implementation, I expect performance of node allocation can be
> improved in the long-term after filesystem image is mounted.
>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
> fs/f2fs/debug.c | 2 +
> fs/f2fs/f2fs.h | 2 +
> fs/f2fs/node.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++--
> include/linux/f2fs_fs.h | 1 +
> 4 files changed, 111 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> index 015ad2b73a92..a77df377e2e8 100644
> --- a/fs/f2fs/debug.c
> +++ b/fs/f2fs/debug.c
> @@ -194,6 +194,8 @@ static void update_mem_info(struct f2fs_sb_info *sbi)
> si->base_mem += sizeof(struct f2fs_nm_info);
> si->base_mem += __bitmap_size(sbi, NAT_BITMAP);
> si->base_mem += (NM_I(sbi)->nat_bits_blocks << F2FS_BLKSIZE_BITS);
> + si->base_mem += NM_I(sbi)->nat_blocks * NAT_ENTRY_BITMAP_SIZE;
> + si->base_mem += NM_I(sbi)->nat_blocks / 8;
>
> get_cache:
> si->cache_mem = 0;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 1c9f0cc8f027..6a48e649bfef 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -556,6 +556,8 @@ struct f2fs_nm_info {
> unsigned int nid_cnt[MAX_NID_LIST]; /* the number of free node id */
> spinlock_t nid_list_lock; /* protect nid lists ops */
> struct mutex build_lock; /* lock for build free nids */
> + unsigned char (*free_nid_bitmap)[NAT_ENTRY_BITMAP_SIZE];
> + unsigned char *nat_block_bitmap;
>
> /* for checkpoint */
> char *nat_bitmap; /* NAT bitmap pointer */
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index b63bdb85ad66..f0f036c2d2fc 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1821,14 +1821,32 @@ static void remove_free_nid(struct f2fs_sb_info *sbi, nid_t nid)
> kmem_cache_free(free_nid_slab, i);
> }
>
> +void update_free_nid_bitmap(struct f2fs_sb_info *sbi, nid_t nid, bool set)
> +{
> + struct f2fs_nm_info *nm_i = NM_I(sbi);
> + unsigned int nat_ofs = NAT_BLOCK_OFFSET(nid);
> + unsigned int nid_ofs = nid - START_NID(nid);
> +
> + if (!test_bit_le(nat_ofs, nm_i->nat_block_bitmap))
> + return;
> +
> + if (set)
> + set_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
> + else
> + clear_bit_le(nid_ofs, nm_i->free_nid_bitmap[nat_ofs]);
> +}
> +
> static void scan_nat_page(struct f2fs_sb_info *sbi,
> struct page *nat_page, nid_t start_nid)
> {
> struct f2fs_nm_info *nm_i = NM_I(sbi);
> struct f2fs_nat_block *nat_blk = page_address(nat_page);
> block_t blk_addr;
> + unsigned int nat_ofs = NAT_BLOCK_OFFSET(start_nid);
> int i;
>
> + set_bit_le(nat_ofs, nm_i->nat_block_bitmap);
> +
> i = start_nid % NAT_ENTRY_PER_BLOCK;
>
> for (; i < NAT_ENTRY_PER_BLOCK; i++, start_nid++) {
> @@ -1840,7 +1858,51 @@ static void scan_nat_page(struct f2fs_sb_info *sbi,
> f2fs_bug_on(sbi, blk_addr == NEW_ADDR);
> if (blk_addr == NULL_ADDR)
> add_free_nid(sbi, start_nid, true);
> + update_free_nid_bitmap(sbi, start_nid, blk_addr == NULL_ADDR);
> + }
> +}
> +
> +static void scan_free_nid_bits(struct f2fs_sb_info *sbi)
> +{
> + struct f2fs_nm_info *nm_i = NM_I(sbi);
> + struct curseg_info *curseg = CURSEG_I(sbi, CURSEG_HOT_DATA);
> + struct f2fs_journal *journal = curseg->journal;
> + unsigned int i, idx;
> + unsigned int target = FREE_NID_PAGES * NAT_ENTRY_PER_BLOCK;
> +
> + down_read(&nm_i->nat_tree_lock);
> +
> + for (i = 0; i < nm_i->nat_blocks; i++) {
> + if (!test_bit_le(i, nm_i->nat_block_bitmap))
> + continue;
> + for (idx = 0; idx < NAT_ENTRY_PER_BLOCK; idx++) {
> + nid_t nid;
> +
> + if (!test_bit_le(idx, nm_i->free_nid_bitmap[i]))
> + continue;
> +
> + nid = i * NAT_ENTRY_PER_BLOCK + idx;
> + add_free_nid(sbi, nid, true);
> +
> + if (nm_i->nid_cnt[FREE_NID_LIST] >= target)
> + goto out;
> + }
> + }
> +out:
> + down_read(&curseg->journal_rwsem);
> + for (i = 0; i < nats_in_cursum(journal); i++) {
> + block_t addr;
> + nid_t nid;
> +
> + addr = le32_to_cpu(nat_in_journal(journal, i).block_addr);
> + nid = le32_to_cpu(nid_in_journal(journal, i));
> + if (addr == NULL_ADDR)
> + add_free_nid(sbi, nid, true);
> + else
> + remove_free_nid(sbi, nid);
> }
> + up_read(&curseg->journal_rwsem);
> + up_read(&nm_i->nat_tree_lock);
> }
>
> static int scan_nat_bits(struct f2fs_sb_info *sbi)
> @@ -1910,9 +1972,17 @@ static void __build_free_nids(struct f2fs_sb_info *sbi, bool sync, bool mount)
> if (!sync && !available_free_memory(sbi, FREE_NIDS))
> return;
>
> - /* try to find free nids with nat_bits */
> - if (!mount && !scan_nat_bits(sbi) && nm_i->nid_cnt[FREE_NID_LIST])
> - return;
> + if (!mount) {
> + /* try to find free nids in free_nid_bitmap */
> + scan_free_nid_bits(sbi);
> +
> + if (nm_i->nid_cnt[FREE_NID_LIST])
> + return;
> +
> + /* try to find free nids with nat_bits */
> + if (!scan_nat_bits(sbi) && nm_i->nid_cnt[FREE_NID_LIST])
> + return;
> + }
>
> /* find next valid candidate */
> if (is_set_ckpt_flags(sbi, CP_NAT_BITS_FLAG)) {
> @@ -2005,6 +2075,9 @@ bool alloc_nid(struct f2fs_sb_info *sbi, nid_t *nid)
> i->state = NID_ALLOC;
> __insert_nid_to_list(sbi, i, ALLOC_NID_LIST, false);
> nm_i->available_nids--;
> +
> + update_free_nid_bitmap(sbi, *nid, false);
> +
> spin_unlock(&nm_i->nid_list_lock);
> return true;
> }
> @@ -2059,6 +2132,8 @@ void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid)
>
> nm_i->available_nids++;
>
> + update_free_nid_bitmap(sbi, nid, true);
> +
> spin_unlock(&nm_i->nid_list_lock);
>
> if (need_free)
> @@ -2387,6 +2462,11 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
> add_free_nid(sbi, nid, false);
> spin_lock(&NM_I(sbi)->nid_list_lock);
> NM_I(sbi)->available_nids++;
> + update_free_nid_bitmap(sbi, nid, true);
> + spin_unlock(&NM_I(sbi)->nid_list_lock);
> + } else {
> + spin_lock(&NM_I(sbi)->nid_list_lock);
> + update_free_nid_bitmap(sbi, nid, false);
> spin_unlock(&NM_I(sbi)->nid_list_lock);
> }
> }
> @@ -2556,6 +2636,22 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
> return 0;
> }
>
> +int init_free_nid_cache(struct f2fs_sb_info *sbi)
> +{
> + struct f2fs_nm_info *nm_i = NM_I(sbi);
> +
> + nm_i->free_nid_bitmap = f2fs_kvzalloc(nm_i->nat_blocks *
> + NAT_ENTRY_BITMAP_SIZE, GFP_KERNEL);
> + if (!nm_i->free_nid_bitmap)
> + return -ENOMEM;
> +
> + nm_i->nat_block_bitmap = f2fs_kvzalloc(nm_i->nat_blocks / 8,
> + GFP_KERNEL);
> + if (!nm_i->nat_block_bitmap)
> + return -ENOMEM;
> + return 0;
> +}
> +
> int build_node_manager(struct f2fs_sb_info *sbi)
> {
> int err;
> @@ -2568,6 +2664,10 @@ int build_node_manager(struct f2fs_sb_info *sbi)
> if (err)
> return err;
>
> + err = init_free_nid_cache(sbi);
> + if (err)
> + return err;
> +
> build_free_nids(sbi, true, true);
> return 0;
> }
> @@ -2626,6 +2726,9 @@ void destroy_node_manager(struct f2fs_sb_info *sbi)
> }
> up_write(&nm_i->nat_tree_lock);
>
> + kvfree(nm_i->nat_block_bitmap);
> + kvfree(nm_i->free_nid_bitmap);
> +
> kfree(nm_i->nat_bitmap);
> kfree(nm_i->nat_bits);
> #ifdef CONFIG_F2FS_CHECK_FS
> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> index 1c92ace2e8f8..e2d239ed4c60 100644
> --- a/include/linux/f2fs_fs.h
> +++ b/include/linux/f2fs_fs.h
> @@ -279,6 +279,7 @@ struct f2fs_node {
> * For NAT entries
> */
> #define NAT_ENTRY_PER_BLOCK (PAGE_SIZE / sizeof(struct f2fs_nat_entry))
> +#define NAT_ENTRY_BITMAP_SIZE ((NAT_ENTRY_PER_BLOCK + 7) / 8)
>
> struct f2fs_nat_entry {
> __u8 version; /* latest version of cached nat entry */
> --
> 2.8.2.295.g3f1c1d0
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