On Fri, Jan 18, 2013 at 12:39:47AM -0500, Theodore Ts'o wrote:
> On Fri, Jan 18, 2013 at 12:19:21AM -0500, Theodore Ts'o wrote:
> > I'm a bit concerned we might be too aggressive,
> > because there are two ways that items can be freed from the
> > extent_status tree. One is if the inode is not used at all, and when
> > we release the inode, we'll drop all of the entries in the
> > extent_status_tree for that inode. The second way is via the shrinker
> > which we've registered.
>
> If we use the sb->s_op->free_cached_objects() approach, something like
> the following change to prune_super() in fs/super.c might address the
> above concern:
Sorry for delay reply. I believe that sb->s_op->free_cached_objbects()
approach is better. So in next version I will try to implement this approach.
>
> diff --git a/fs/super.c b/fs/super.c
> index 12f1237..fb57bd2 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -80,6 +80,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
> if (sc->nr_to_scan) {
> int dentries;
> int inodes;
> + int fs_to_scan = 0;
>
> /* proportion the scan between the caches */
> dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) /
> @@ -87,7 +88,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
> inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) /
> total_objects;
> if (fs_objects)
> - fs_objects = (sc->nr_to_scan * fs_objects) /
> + fs_to_scan = (sc->nr_to_scan * fs_objects) /
> total_objects;
> /*
> * prune the dcache first as the icache is pinned by it, then
> @@ -96,8 +97,23 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
> prune_dcache_sb(sb, dentries);
> prune_icache_sb(sb, inodes);
>
> - if (fs_objects && sb->s_op->free_cached_objects) {
> - sb->s_op->free_cached_objects(sb, fs_objects);
> + /*
> + * If as a result of pruning the icache, we released some
> + * of the fs_objects, give credit to the fact and
> + * reduce the number of fs objects that we should try
> + * to release.
> + */
> + if (fs_to_scan) {
> + int fs_objects_now = sb->s_op->nr_cached_objects(sb);
> +
> + if (fs_objects_now < fs_objects)
> + fs_to_scan -= fs_objects - fs_objects_now;
> + if (fs_to_scan < 0)
> + fs_to_scan = 0;
> + }
> +
> + if (fs_to_scan && sb->s_op->free_cached_objects) {
> + sb->s_op->free_cached_objects(sb, fs_to_scan);
> fs_objects = sb->s_op->nr_cached_objects(sb);
> }
> total_objects = sb->s_nr_dentry_unused +
>
> What do folks think?
Do we need to CC' linux-fsdevel mailling list to let other folks review
this patch?
Thanks,
- Zheng
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