Messages in this thread | | | From | Chao Yu <> | Subject | RE: [f2fs-dev][RFC PATCH 06/10] f2fs: add core functions for rb-tree extent cache | Date | Fri, 23 Jan 2015 14:15:56 +0800 |
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Hi Jaegeuk,
> -----Original Message----- > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org] > Sent: Friday, January 23, 2015 9:48 AM > To: Chao Yu > Cc: Changman Lee; linux-f2fs-devel@lists.sourceforge.net; linux-kernel@vger.kernel.org > Subject: Re: [f2fs-dev][RFC PATCH 06/10] f2fs: add core functions for rb-tree extent cache > > On Mon, Jan 12, 2015 at 03:14:48PM +0800, Chao Yu wrote: > > This patch adds core functions including slab cache init function and > > init/lookup/update/shrink/destroy function for rb-tree based extent cache. > > > > Thank Jaegeuk Kim and Changman Lee as they gave much suggestion about detail > > design and implementation of extent cache. > > > > Todo: > > * add a cached_ei into struct extent_tree for a quick recent cache. > > * register rb-based extent cache shrink with mm shrink interface. > > * disable dir inode's extent cache. > > > > Signed-off-by: Chao Yu <chao2.yu@samsung.com> > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > > Signed-off-by: Changman Lee <cm224.lee@samsung.com> > > --- > > fs/f2fs/data.c | 458 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > fs/f2fs/node.c | 9 +- > > 2 files changed, 466 insertions(+), 1 deletion(-) > > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > > index 4f5b871e..bf8c5eb 100644 > > --- a/fs/f2fs/data.c > > +++ b/fs/f2fs/data.c > > @@ -25,6 +25,9 @@ > > #include "trace.h" > > #include <trace/events/f2fs.h> > > > > +struct kmem_cache *extent_tree_slab; > > +struct kmem_cache *extent_node_slab; > > + > > static void f2fs_read_end_io(struct bio *bio, int err) > > { > > struct bio_vec *bvec; > > @@ -373,6 +376,430 @@ end_update: > > return need_update; > > } > > > > +static struct extent_node *__lookup_extent_tree(struct extent_tree *et, > > + unsigned int fofs) > > +{ > > + struct rb_node *node = et->root.rb_node; > > + struct extent_node *en; > > + > > + while (node) { > > + en = rb_entry(node, struct extent_node, rb_node); > > + if (fofs < en->ei.fofs) > > + node = node->rb_left; > > + else if (fofs >= en->ei.fofs + en->ei.len) > > + node = node->rb_right; > > + else > > + return en; > > + } > > + return NULL; > > +} > > + > > +static inline void set_extent_info(struct extent_info *ei, unsigned int fofs, > > + u32 blk, unsigned int len) > > +{ > > + ei->fofs = fofs; > > + ei->blk = blk; > > + ei->len = len; > > +} > > + > > +static inline bool __is_extent_mergeable(struct extent_info *back, > > + struct extent_info *front) > > +{ > > + return (back->fofs + back->len == front->fofs && > > + back->blk + back->len == front->blk); > > +} > > + > > +static bool __is_back_mergeable(struct extent_info *cur, > > + struct extent_info *back) > > +{ > > + return __is_extent_mergeable(back, cur); > > +} > > + > > +static bool __is_front_mergeable(struct extent_info *cur, > > + struct extent_info *front) > > +{ > > + return __is_extent_mergeable(cur, front); > > +} > > > How about declaring these four functions as inline ones and locating them > inside f2fs.h?
Good idea! Will do.
> > > + > > +static struct extent_node *__try_back_merge(struct extent_tree *et, > > + struct extent_node *en) > > +{ > > + struct extent_node *prev; > > + struct rb_node *node; > > + > > + node = rb_prev(&en->rb_node); > > + if (!node) > > + return NULL; > > + > > + prev = rb_entry(node, struct extent_node, rb_node); > > + if (__is_back_mergeable(&en->ei, &prev->ei)) { > > + en->ei.fofs = prev->ei.fofs; > > + en->ei.blk = prev->ei.blk; > > + en->ei.len += prev->ei.len; > > + rb_erase(&prev->rb_node, &et->root); > > + et->count--; > > + return prev; > > + } > > + return NULL; > > +} > > + > > +static struct extent_node *__try_front_merge(struct extent_tree *et, > > + struct extent_node *en) > > +{ > > + struct extent_node *next; > > + struct rb_node *node; > > + > > + node = rb_next(&en->rb_node); > > + if (!node) > > + return NULL; > > + > > + next = rb_entry(node, struct extent_node, rb_node); > > + if (__is_front_mergeable(&en->ei, &next->ei)) { > > + en->ei.len += next->ei.len; > > + rb_erase(&next->rb_node, &et->root); > > + et->count--; > > + return next; > > + } > > + return NULL; > > +} > > + > > +static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi, > > + struct extent_tree *et, struct extent_info *ei, > > + struct extent_node **den) > > +{ > > + struct rb_node **p = &et->root.rb_node; > > + struct rb_node *parent = NULL; > > + struct extent_node *en; > > + > > + while (*p) { > > + parent = *p; > > + en = rb_entry(parent, struct extent_node, rb_node); > > + > > + if (ei->fofs < en->ei.fofs) { > > + if (__is_front_mergeable(ei, &en->ei)) { > > + f2fs_bug_on(sbi, !den); > > + en->ei.fofs = ei->fofs; > > + en->ei.blk = ei->blk; > > + en->ei.len += ei->len; > > + *den = __try_back_merge(et, en); > > + return en; > > + } > > + p = &(*p)->rb_left; > > + } else if (ei->fofs >= en->ei.fofs + en->ei.len) { > > + if (__is_back_mergeable(ei, &en->ei)) { > > + f2fs_bug_on(sbi, !den); > > + en->ei.len += ei->len; > > + *den = __try_front_merge(et, en); > > + return en; > > + } > > + p = &(*p)->rb_right; > > + } else > > + f2fs_bug_on(F2FS_I_SB(inode), 1); > > Coding style. > > } else { > ... > }
will fix.
> > > + } > > How about adding __attach_extent_node()?
That's more readable.
How do you think of the following functions:
struct extent_node *__attach_extent_node(struct f2fs_sb_info *sbi, struct extent_tree *et, struct extent_info *ei, struct rb_node *parent, struct rb_node **p) { struct extent_node *en;
en = kmem_cache_alloc(extent_node_slab, GFP_ATOMIC); if (!en) return NULL;
en->ei = *ei; INIT_LIST_HEAD(&en->list);
rb_link_node(&en->rb_node, parent, p); rb_insert_color(&en->rb_node, &et->root); et->count++; atomic_inc(&sbi->total_ext_node); return en; }
static void __detach_extent_node(struct f2fs_sb_info *sbi, struct extent_tree *et, struct extent_node *en) { rb_erase(&en->rb_node, &et->root); et->count--; atomic_dec(&sbi->total_ext_node); }
> { > > + > > + en = kmem_cache_alloc(extent_node_slab, GFP_ATOMIC); > > en = f2fs_kmem_cache_alloc(.., GFP_ATOMIC);
We should avoid cond_resched() in f2fs_kmem_cache_alloc when we are holding write_lock.
IMO, it's better to return NULL if we fail to alloc extent_node here. Otherwise we'd better alloc extent_node before write_lock.
> > > + en->ei = *ei; > > + INIT_LIST_HEAD(&en->list); > > + > > + rb_link_node(&en->rb_node, parent, p); > > + rb_insert_color(&en->rb_node, &et->root); > > + atomic_inc(&sbi->total_ext_node); > > + et->count++; > > } > > > + > > + return en; > > +} > > + > > +static struct extent_node *__remove_extent_tree(struct extent_tree *et, > > + unsigned int fofs) > > This is __detach_extent_node()? > > > +{ > > + struct rb_node *p = et->root.rb_node; > > + struct extent_node *en; > > + > > + while (p) { > > + en = rb_entry(p, struct extent_node, rb_node); > > + > > + if (fofs < en->ei.fofs) > > + p = p->rb_left; > > Coding style. > > if () { > } else { > }
will fix.
> > > + else if (fofs >= en->ei.fofs + en->ei.len) > > + p = p->rb_right; > > + else { > > + rb_erase(&en->rb_node, &et->root); > > + et->count--; > > Add here? > atomic_dec(&sbi->total_ext_node);
Agree, see __detach_extent_node() implementation above.
> > > + return en; > > + } > > + } > > + return NULL; > > +} > > + > > +static unsigned int __free_extent_tree(struct f2fs_sb_info *sbi, > > + struct extent_tree *et, bool free_all) > > +{ > > + struct rb_node *node, *next; > > + struct extent_node *en; > > + unsigned int count = et->count; > > + > > + node = rb_first(&et->root); > > + while (node) { > > + next = rb_next(node); > > + en = rb_entry(node, struct extent_node, rb_node); > > + > > + if (free_all) { > > + spin_lock(&sbi->extent_lock); > > + if (!list_empty(&en->list)) > > + list_del_init(&en->list); > > + spin_unlock(&sbi->extent_lock); > > + } > > + > > + if (free_all || list_empty(&en->list)) { > > + rb_erase(node, &et->root); > > + kmem_cache_free(extent_node_slab, en); > > + atomic_dec(&sbi->total_ext_node); > > + et->count--; > > + } > > + node = next; > > + } > > + > > + return count - et->count; > > +} > > + > > +static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs, > > + struct extent_info *ei) > > +{ > > + struct f2fs_sb_info *sbi = F2FS_I_SB(inode); > > + struct extent_tree *et; > > + struct extent_node *en; > > + > > + if (is_inode_flag_set(F2FS_I(inode), FI_NO_EXTENT)) > > + return false; > > + > > + down_read(&sbi->extent_tree_lock); > > + et = radix_tree_lookup(&sbi->extent_tree_root, inode->i_ino); > > + if (!et) { > > + up_read(&sbi->extent_tree_lock); > > + return false; > > + } > > + atomic_inc(&et->refcount); > > + up_read(&sbi->extent_tree_lock); > > + > > + read_lock(&et->lock); > > + en = __lookup_extent_tree(et, pgofs); > > + if (en) { > > + *ei = en->ei; > > + spin_lock(&sbi->extent_lock); > > + if (!list_empty(&en->list)) > > + list_move_tail(&en->list, &sbi->extent_list); > > + spin_unlock(&sbi->extent_lock); > > + stat_inc_read_hit(sbi->sb); > > + } > > + stat_inc_total_hit(sbi->sb); > > + read_unlock(&et->lock); > > + > > + atomic_dec(&et->refcount); > > + return en ? true : false; > > +} > > + > > +static void f2fs_update_extent_tree(struct inode *inode, pgoff_t fofs, > > + block_t blkaddr) > > +{ > > + struct f2fs_sb_info *sbi = F2FS_I_SB(inode); > > + nid_t ino = inode->i_ino; > > + struct extent_tree *et; > > + struct extent_node *en = NULL, *en1 = NULL, *en2 = NULL, *en3 = NULL; > > + struct extent_node *den = NULL; > > + struct extent_info *pei; > > + struct extent_info ei; > > + unsigned int endofs; > > + > > + if (is_inode_flag_set(F2FS_I(inode), FI_NO_EXTENT)) > > + return; > > + > > +retry: > > + down_write(&sbi->extent_tree_lock); > > + et = radix_tree_lookup(&sbi->extent_tree_root, ino); > > + if (!et) { > > + et = kmem_cache_alloc(extent_tree_slab, GFP_ATOMIC); > > et = f2fs_kmem_cache_alloc(.., GFP_ATOMIC);
How about modifying as below to avoid holding extent_tree_lock for long time?
et = kmem_cache_alloc(extent_tree_slab, GFP_ATOMIC); if (!et) { up_write(&sbi->extent_tree_lock); cond_resched(); goto retry; }
> > > + if (!et) { > > + up_write(&sbi->extent_tree_lock); > > + goto retry; > > + } > > + if (radix_tree_insert(&sbi->extent_tree_root, ino, et)) { > > + up_write(&sbi->extent_tree_lock); > > + kmem_cache_free(extent_tree_slab, et);
cond_resched()?
> > + goto retry; > > + } > > + memset(et, 0, sizeof(struct extent_tree)); > > + et->ino = ino; > > + et->root = RB_ROOT; > > + rwlock_init(&et->lock); > > + atomic_set(&et->refcount, 0); > > + et->count = 0; > > + sbi->total_ext_tree++; > > + } > > + atomic_inc(&et->refcount); > > + up_write(&sbi->extent_tree_lock); > > + > > + write_lock(&et->lock); > > + > > + /* 1. lookup and remove exist extent info in cache */ > > existing
got it.
> > > + en = __remove_extent_tree(et, fofs); > > en = __detach_extent_node();?
OK, it seems that most codes of __remove_extent_tree and __lookup_extent_tree are the same, so here I want to remove extent node like this:
en = __lookup_extent_tree(et, fofs); if (!en) goto update_extent;
dei = en->ei; __detach_extent_node(sbi, et, en);
How do you think?
> > > + if (!en) > > + goto update_extent; > > + > > + pei = &en->ei; > > + /* 2. if extent can be split more, split and insert the left part */ > > + if (pei->len > 1) { > > + /* insert left part of split extent into cache */ > > + if (pei->fofs < fofs) { > > + set_extent_info(&ei, pei->fofs, pei->blk, > > + fofs - pei->fofs); > > + en1 = __insert_extent_tree(sbi, et, &ei, NULL); > > + } > > + > > + /* insert right part of split extent into cache */ > > + endofs = pei->fofs + pei->len - 1; > > + if (endofs > fofs) { > > + set_extent_info(&ei, fofs + 1, > > + fofs - pei->fofs + pei->blk, endofs - fofs); > > + en2 = __insert_extent_tree(sbi, et, &ei, NULL); > > + } > > + } > > + > > +update_extent: > > + /* 3. update extent in extent cache */ > > + if (blkaddr) { > > + set_extent_info(&ei, fofs, blkaddr, 1); > > + en3 = __insert_extent_tree(sbi, et, &ei, &den); > > + } > > + > > + /* 4. update in global extent list */ > > + spin_lock(&sbi->extent_lock); > > + if (en && !list_empty(&en->list)) > > + list_del_init(&en->list); > > + /* > > + * en1 and en2 split from en, they will become more and more smaller > > + * fragments after splitting several times. So if the length is smaller > > + * than F2FS_MIN_EXTENT_LEN, we will not add them into extent_list, > > + * but just waiting shrinker to free them for reclaiming when OOM. > > + */ > > Can we just remove en1 and en2 in __insert_extent_tree?
en1 and en2 is newly added, in __attach_extent_node we do not add en1 and en2 into lru list, so if you do not want to keep split part in lru list, let's just remove the below codes.
> > > + if (en1 && en1->ei.len >= F2FS_MIN_EXTENT_LEN) > > + list_add_tail(&en1->list, &sbi->extent_list); > > + if (en2 && en2->ei.len >= F2FS_MIN_EXTENT_LEN) > > + list_add_tail(&en2->list, &sbi->extent_list); > > + if (en3) { > > + if (list_empty(&en3->list)) > > + list_add_tail(&en3->list, &sbi->extent_list); > > + else > > + list_move_tail(&en3->list, &sbi->extent_list); > > + } > > + if (den && !list_empty(&den->list)) > > + list_del_init(&den->list); > > + spin_unlock(&sbi->extent_lock); > > + > > + if (en) { > > + kmem_cache_free(extent_node_slab, en); > > + atomic_dec(&sbi->total_ext_node); > > --> move into __detach_extent_node().
will do.
> > > + } > > + if (den) { > > + kmem_cache_free(extent_node_slab, den); > > + atomic_dec(&sbi->total_ext_node); > > + } > > + > > + write_unlock(&et->lock); > > + atomic_dec(&et->refcount); > > +} > > + > > +void f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink) > > +{ > > + struct extent_tree *treevec[EXT_TREE_VEC_SIZE]; > > + struct extent_node *en, *tmp; > > + unsigned long ino = F2FS_ROOT_INO(sbi); > > + struct radix_tree_iter iter; > > + void **slot; > > + unsigned int found; > > + unsigned int node_cnt = 0, tree_cnt = 0; > > + > > + if (available_free_memory(sbi, EXTENT_CACHE)) > > + return; > > + > > + spin_lock(&sbi->extent_lock); > > + list_for_each_entry_safe(en, tmp, &sbi->extent_list, list) { > > + if (!nr_shrink--) > > + break; > > + list_del_init(&en->list); > > + } > > + spin_unlock(&sbi->extent_lock); > > + > > + down_read(&sbi->extent_tree_lock); > > + while ((found = radix_tree_gang_lookup(&sbi->extent_tree_root, > > + (void **)treevec, ino, EXT_TREE_VEC_SIZE))) { > > + unsigned i; > > + > > + ino = treevec[found - 1]->ino + 1; > > + for (i = 0; i < found; i++) { > > + struct extent_tree *et = treevec[i]; > > + > > + atomic_inc(&et->refcount); > > + write_lock(&et->lock); > > + node_cnt += __free_extent_tree(sbi, et, false); > > + write_unlock(&et->lock); > > + atomic_dec(&et->refcount); > > + } > > + } > > + up_read(&sbi->extent_tree_lock); > > + > > + down_write(&sbi->extent_tree_lock); > > + radix_tree_for_each_slot(slot, &sbi->extent_tree_root, &iter, > > + F2FS_ROOT_INO(sbi)) { > > + struct extent_tree *et = (struct extent_tree *)*slot; > > + > > + if (!atomic_read(&et->refcount) && !et->count) { > > + radix_tree_delete(&sbi->extent_tree_root, et->ino); > > + kmem_cache_free(extent_tree_slab, et); > > + sbi->total_ext_tree--; > > + tree_cnt++; > > No use of tree_cnt.
This is used by trace function in RFC PATCH 10/10.
Thanks for your review! :)
Regards, Yu
> > Thanks,
[snip]
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