[Cluster-devel] [GFS2 PATCH] GFS2: Don't waste time locking lru_lock for non-lru glocks

[Bob Peterson <rpeterso@redhat.com>]

Hi,

Before this patch, glock_dq would call gfs2_glock_remove_from_lru.
For glocks that are never put on the LRU, such as the transaction
glock, this just takes the spin_lock, determines there's nothing to
be done because the list is empty, then unlocks again. This was
causing unnecessary lock contention on the lru_lock spin_lock.
This patch adds a check for GLOF_LRU in the glops before taking
the spin_lock, thus reducing lru_lock contention.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index c38ab6c81898..1029340fc8ba 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -150,6 +150,9 @@ void gfs2_glock_add_to_lru(struct gfs2_glock *gl)
 
 static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
 {
+	if (!(gl->gl_ops->go_flags & GLOF_LRU))
+		return;
+
 	spin_lock(&lru_lock);
 	if (!list_empty(&gl->gl_lru)) {
 		list_del_init(&gl->gl_lru);