Re: [f2fs-dev] [PATCH 1/2] f2fs: use atomic variable for total_extent_tree

[Jaegeuk Kim <jaegeuk@kernel.org>]

On Tue, Dec 22, 2015 at 01:28:09PM +0800, Chao Yu wrote:
> Hi Jaegeuk,
> 
> > -----Original Message-----
> > From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> > Sent: Tuesday, December 22, 2015 11:39 AM
> > To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> > linux-f2fs-devel@lists.sourceforge.net
> > Cc: Jaegeuk Kim
> > Subject: [f2fs-dev] [PATCH 1/2] f2fs: use atomic variable for total_extent_tree
> > 
> > It would be better to use atomic variable for total_extent_tree.
> 
> total_extent_tree was protected by extent_tree_lock semaphore, so intention here
> is to make related calculation in available_free_memory or update_general_status
> more accurate, right?

Moreover, another major thing is to specify it is atomic along with other extent
counts.

Thanks,

> 
> Thanks,
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/debug.c        | 5 +++--
> >  fs/f2fs/extent_cache.c | 8 ++++----
> >  fs/f2fs/f2fs.h         | 2 +-
> >  fs/f2fs/node.c         | 3 ++-
> >  fs/f2fs/shrinker.c     | 3 ++-
> >  5 files changed, 12 insertions(+), 9 deletions(-)
> > 
> > diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
> > index bb307e6..ed5dfcc 100644
> > --- a/fs/f2fs/debug.c
> > +++ b/fs/f2fs/debug.c
> > @@ -38,7 +38,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
> >  	si->hit_rbtree = atomic64_read(&sbi->read_hit_rbtree);
> >  	si->hit_total = si->hit_largest + si->hit_cached + si->hit_rbtree;
> >  	si->total_ext = atomic64_read(&sbi->total_hit_ext);
> > -	si->ext_tree = sbi->total_ext_tree;
> > +	si->ext_tree = atomic_read(&sbi->total_ext_tree);
> >  	si->ext_node = atomic_read(&sbi->total_ext_node);
> >  	si->ndirty_node = get_pages(sbi, F2FS_DIRTY_NODES);
> >  	si->ndirty_dent = get_pages(sbi, F2FS_DIRTY_DENTS);
> > @@ -193,7 +193,8 @@ get_cache:
> >  	si->cache_mem += si->inmem_pages * sizeof(struct inmem_pages);
> >  	for (i = 0; i <= UPDATE_INO; i++)
> >  		si->cache_mem += sbi->im[i].ino_num * sizeof(struct ino_entry);
> > -	si->cache_mem += sbi->total_ext_tree * sizeof(struct extent_tree);
> > +	si->cache_mem += atomic_read(&sbi->total_ext_tree) *
> > +						sizeof(struct extent_tree);
> >  	si->cache_mem += atomic_read(&sbi->total_ext_node) *
> >  						sizeof(struct extent_node);
> > 
> > diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
> > index e86e9f1e..0e97d6af 100644
> > --- a/fs/f2fs/extent_cache.c
> > +++ b/fs/f2fs/extent_cache.c
> > @@ -70,7 +70,7 @@ static struct extent_tree *__grab_extent_tree(struct inode *inode)
> >  		rwlock_init(&et->lock);
> >  		atomic_set(&et->refcount, 0);
> >  		et->count = 0;
> > -		sbi->total_ext_tree++;
> > +		atomic_inc(&sbi->total_ext_tree);
> >  	}
> >  	atomic_inc(&et->refcount);
> >  	up_write(&sbi->extent_tree_lock);
> > @@ -570,7 +570,7 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int
> > nr_shrink)
> > 
> >  				radix_tree_delete(root, et->ino);
> >  				kmem_cache_free(extent_tree_slab, et);
> > -				sbi->total_ext_tree--;
> > +				atomic_dec(&sbi->total_ext_tree);
> >  				tree_cnt++;
> > 
> >  				if (node_cnt + tree_cnt >= nr_shrink)
> > @@ -663,7 +663,7 @@ void f2fs_destroy_extent_tree(struct inode *inode)
> >  	f2fs_bug_on(sbi, atomic_read(&et->refcount) || et->count);
> >  	radix_tree_delete(&sbi->extent_tree_root, inode->i_ino);
> >  	kmem_cache_free(extent_tree_slab, et);
> > -	sbi->total_ext_tree--;
> > +	atomic_dec(&sbi->total_ext_tree);
> >  	up_write(&sbi->extent_tree_lock);
> > 
> >  	F2FS_I(inode)->extent_tree = NULL;
> > @@ -715,7 +715,7 @@ void init_extent_cache_info(struct f2fs_sb_info *sbi)
> >  	init_rwsem(&sbi->extent_tree_lock);
> >  	INIT_LIST_HEAD(&sbi->extent_list);
> >  	spin_lock_init(&sbi->extent_lock);
> > -	sbi->total_ext_tree = 0;
> > +	atomic_set(&sbi->total_ext_tree, 0);
> >  	atomic_set(&sbi->total_ext_node, 0);
> >  }
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 19beabe..a7f6191 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -762,7 +762,7 @@ struct f2fs_sb_info {
> >  	struct rw_semaphore extent_tree_lock;	/* locking extent radix tree */
> >  	struct list_head extent_list;		/* lru list for shrinker */
> >  	spinlock_t extent_lock;			/* locking extent lru list */
> > -	int total_ext_tree;			/* extent tree count */
> > +	atomic_t total_ext_tree;		/* extent tree count */
> >  	atomic_t total_ext_node;		/* extent info count */
> > 
> >  	/* basic filesystem units */
> > diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> > index d842b19..6cc8ac7 100644
> > --- a/fs/f2fs/node.c
> > +++ b/fs/f2fs/node.c
> > @@ -65,7 +65,8 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int type)
> >  				sizeof(struct ino_entry)) >> PAGE_CACHE_SHIFT;
> >  		res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 1);
> >  	} else if (type == EXTENT_CACHE) {
> > -		mem_size = (sbi->total_ext_tree * sizeof(struct extent_tree) +
> > +		mem_size = (atomic_read(&sbi->total_ext_tree) *
> > +				sizeof(struct extent_tree) +
> >  				atomic_read(&sbi->total_ext_node) *
> >  				sizeof(struct extent_node)) >> PAGE_CACHE_SHIFT;
> >  		res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 1);
> > diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
> > index da0d8e0..a11e099 100644
> > --- a/fs/f2fs/shrinker.c
> > +++ b/fs/f2fs/shrinker.c
> > @@ -32,7 +32,8 @@ static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
> > 
> >  static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
> >  {
> > -	return sbi->total_ext_tree + atomic_read(&sbi->total_ext_node);
> > +	return atomic_read(&sbi->total_ext_tree) +
> > +				atomic_read(&sbi->total_ext_node);
> >  }
> > 
> >  unsigned long f2fs_shrink_count(struct shrinker *shrink,
> > --
> > 2.5.4 (Apple Git-61)
> > 
> > 
> > ------------------------------------------------------------------------------
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