On 2017/5/20 20:24, Hou Pengyang wrote:
> during flush_nat_entries, we do:
> 1) gang_lookup a radix tree, find all the dirty nat_entry_set;
> 2) sort nat_entry_set by nat_entry_set->entry_cnt, in order to
> write to journal as much as possible to avoid unnessary IO.
>
> This patch optimize the look_up & sort algorithm by introducing an array:
>
> f2fs_nm_info->dirty_set[NAT_ENTRY_PER_BLOCK+1];
> (struct list_head dirty_set[NAT_ENTRY_PER_BLOCK + 1])
>
> dirty_set[1] links all nat_entry_set whose entry_cnt is 1
> dirty_set[2] links all nat_entry_set whose entry_cnt is 2
> ......
> dirty_set[N] links all nat_entry_set whose entry_cnt is N
>
> as one NAT block has NAT_ENTRY_PER_BLOCK entries at MOST, so there should NOT
> be one nat_entry_set whose entry_cnt is larger than NAT_ENTRY_PER_BLOCK.
>
> So it is enough for f2fs_nm_info->dirty_set to link all nat_entry_sets in
> system.
>
> Update:
> we update nat_entry_set in real-time, e.g originally
> nat_entry_set->entry_cnt is
> 1, and licked by dirty_set[1]; then call __set_nat_cache_dirty to increase
> nat_entry'sentry_cnt, we move this nat_entry_set ot dirty_set[2]'s tail, no
> need to compare.
>
> Flush:
> when flush dirty nat_entry_set, we just flush nat_entry_set from
> f2fs_nm_info->dirty_set[0] to f2fs_nm_info->dirty_set[NAT_ENTRY_PER_BLOCK],
> where
> gang_lookup and sort can be avoid.
>
> footprint of this algorithm: sizeof(struct list_head)*NAT_ENTRY_PER_BLOCK
> = 8*455 = 3.6k bytes
>
> Signed-off-by: Hou Pengyang <[email protected]>
> ---
> fs/f2fs/f2fs.h | 2 ++
> fs/f2fs/node.c | 56 ++++++++++++++++++++++----------------------------------
> 2 files changed, 24 insertions(+), 34 deletions(-)
>
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 093d68a..88a96bb 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -628,6 +628,8 @@ struct f2fs_nm_info {
>
> /* for checkpoint */
> char *nat_bitmap; /* NAT bitmap pointer */
> + /* list dirty_set whose */
> + struct list_head dirty_set[NAT_ENTRY_PER_BLOCK + 1]; /* for */
>
> unsigned int nat_bits_blocks; /* # of nat bits blocks */
> unsigned char *nat_bits; /* NAT bits blocks */
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index d22db8c..340c33d 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -174,13 +174,14 @@ static void __set_nat_cache_dirty(struct f2fs_nm_info
> *nm_i,
> list_move_tail(&ne->list, &head->entry_list);
> nm_i->dirty_nat_cnt++;
> head->entry_cnt++;
> + list_move_tail(&head->set_list, &(nm_i->dirty_set[head->entry_cnt]));
> set_nat_flag(ne, IS_DIRTY, true);
> }
>
> static void __clear_nat_cache_dirty(struct f2fs_nm_info *nm_i,
> struct nat_entry_set *set, struct nat_entry *ne)
> {
> - list_move_tail(&ne->list, &nm_i->nat_entries);
> + list_move_tail(&ne->list, &nm_i->nat_entries); /* to be shrinked */
> set_nat_flag(ne, IS_DIRTY, false);
> set->entry_cnt--;
> nm_i->dirty_nat_cnt--;
> @@ -2340,24 +2341,6 @@ static void remove_nats_in_journal(struct f2fs_sb_info
> *sbi)
> up_write(&curseg->journal_rwsem);
> }
>
> -static void __adjust_nat_entry_set(struct nat_entry_set *nes,
> - struct list_head *head, int max)
> -{
> - struct nat_entry_set *cur;
> -
> - if (nes->entry_cnt >= max)
> - goto add_out;
> -
> - list_for_each_entry(cur, head, set_list) {
> - if (cur->entry_cnt >= nes->entry_cnt) {
> - list_add(&nes->set_list, cur->set_list.prev);
> - return;
> - }
> - }
> -add_out:
> - list_add_tail(&nes->set_list, head);
> -}
> -
> static void __update_nat_bits(struct f2fs_sb_info *sbi, nid_t start_nid,
> struct page *page)
> {
> @@ -2460,9 +2443,11 @@ static void __flush_nat_entry_set(struct f2fs_sb_info
> *sbi,
>
> /* Allow dirty nats by node block allocation in write_begin */
> if (!set->entry_cnt) {
> + list_del(&set->set_list);
> radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
> kmem_cache_free(nat_entry_set_slab, set);
> - }
> + } else
> + f2fs_bug_on(sbi, 1);
Should remove this bug_on, because there will be new nat entries allocated
during flush nat entries since we allow buffered write during checkpoint.
Thanks,
> }
>
> /*
> @@ -2473,10 +2458,8 @@ void flush_nat_entries(struct f2fs_sb_info *sbi,
> struct cp_control *cpc)
> 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;
> - struct nat_entry_set *setvec[SETVEC_SIZE];
> struct nat_entry_set *set, *tmp;
> - unsigned int found;
> - nid_t set_idx = 0;
> + int i;
> LIST_HEAD(sets);
>
> if (!nm_i->dirty_nat_cnt)
> @@ -2493,19 +2476,12 @@ void flush_nat_entries(struct f2fs_sb_info *sbi,
> struct cp_control *cpc)
> !__has_cursum_space(journal, nm_i->dirty_nat_cnt, NAT_JOURNAL))
> remove_nats_in_journal(sbi);
>
> - while ((found = __gang_lookup_nat_set(nm_i,
> - set_idx, SETVEC_SIZE, setvec))) {
> - unsigned idx;
> - set_idx = setvec[found - 1]->set + 1;
> - for (idx = 0; idx < found; idx++)
> - __adjust_nat_entry_set(setvec[idx], &sets,
> - MAX_NAT_JENTRIES(journal));
> + for (i = 0; i <= NAT_ENTRY_PER_BLOCK; i++) {
> + list_for_each_entry_safe(set, tmp, &nm_i->dirty_set[i],
> set_list)
> + __flush_nat_entry_set(sbi, set, cpc);
> + f2fs_bug_on(sbi, !list_empty(&nm_i->dirty_set[i]));
> }
>
> - /* flush dirty nats in nat entry set */
> - list_for_each_entry_safe(set, tmp, &sets, set_list)
> - __flush_nat_entry_set(sbi, set, cpc);
> -
> up_write(&nm_i->nat_tree_lock);
> /* Allow dirty nats by node block allocation in write_begin */
> }
> @@ -2668,6 +2644,15 @@ static int init_free_nid_cache(struct f2fs_sb_info
> *sbi)
> return 0;
> }
>
> +static void init_dirty_set_list(struct f2fs_sb_info *sbi)
> +{
> + struct f2fs_nm_info *nm_i = NM_I(sbi);
> + int i;
> +
> + for (i = 0; i <= NAT_ENTRY_PER_BLOCK; i++)
> + INIT_LIST_HEAD(&nm_i->dirty_set[i]);
> +}
> +
> int build_node_manager(struct f2fs_sb_info *sbi)
> {
> int err;
> @@ -2687,6 +2672,9 @@ int build_node_manager(struct f2fs_sb_info *sbi)
> /* load free nid status from nat_bits table */
> load_free_nid_bitmap(sbi);
>
> + /* init dirty set list */
> + init_dirty_set_list(sbi);
> +
> build_free_nids(sbi, true, true);
> return 0;
> }
>
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