This patch adds a fast lookup path for rb-tree extent cache. In this patch we add a recently accessed extent node pointer 'cached_en' in extent tree. In lookup path of extent cache, we will firstly lookup the last accessed extent node which cached_en points, if we do not hit in this node, we will try to lookup extent node in rb-tree.
By this way we can avoid unnecessary slow lookup in rb-tree sometimes. Note that, side-effect of this patch is that we will increase memory cost, because we will store a pointer variable in each struct extent tree additionally. Signed-off-by: Chao Yu <[email protected]> --- fs/f2fs/data.c | 19 ++++++++++++++++--- fs/f2fs/f2fs.h | 1 + 2 files changed, 17 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 4ba1605..112db9c 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -395,6 +395,9 @@ static void __detach_extent_node(struct f2fs_sb_info *sbi, rb_erase(&en->rb_node, &et->root); et->count--; atomic_dec(&sbi->total_ext_node); + + if (et->cached_en == en) + et->cached_en = NULL; } static struct extent_node *__lookup_extent_tree(struct extent_tree *et, @@ -403,15 +406,24 @@ static struct extent_node *__lookup_extent_tree(struct extent_tree *et, struct rb_node *node = et->root.rb_node; struct extent_node *en; + if (et->cached_en) { + struct extent_info *cei = &et->cached_en->ei; + + if (cei->fofs <= fofs && cei->fofs + cei->len > fofs) + return et->cached_en; + } + while (node) { en = rb_entry(node, struct extent_node, rb_node); - if (fofs < en->ei.fofs) + if (fofs < en->ei.fofs) { node = node->rb_left; - else if (fofs >= en->ei.fofs + en->ei.len) + } else if (fofs >= en->ei.fofs + en->ei.len) { node = node->rb_right; - else + } else { + et->cached_en = en; return en; + } } return NULL; } @@ -587,6 +599,7 @@ static void f2fs_update_extent_tree(struct inode *inode, pgoff_t fofs, memset(et, 0, sizeof(struct extent_tree)); et->ino = ino; et->root = RB_ROOT; + et->cached_en = NULL; rwlock_init(&et->lock); atomic_set(&et->refcount, 0); et->count = 0; diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index 9572f7c..47b30de 100644 --- a/fs/f2fs/f2fs.h +++ b/fs/f2fs/f2fs.h @@ -296,6 +296,7 @@ struct extent_node { struct extent_tree { nid_t ino; /* inode number */ struct rb_root root; /* root of extent info rb-tree */ + struct extent_node *cached_en; /* recently accessed extent node */ rwlock_t lock; /* protect extent info rb-tree */ atomic_t refcount; /* reference count of rb-tree */ unsigned int count; /* # of extent node in rb-tree*/ -- 2.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
