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:
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?
- Ted
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