dlm: avoid scanning unchanged toss lists

Keep track of whether a toss list contains any
shrinkable rsbs.  If not, dlm_scand can avoid
scanning the list for rsbs to shrink.  Unnecessary
scanning can otherwise waste a lot of time because
the toss lists can contain a large number of rsbs
that are non-shrinkable (directory records).

Signed-off-by: David Teigland <teigland@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index a579f30f237d..f7501651762d 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -1132,6 +1132,7 @@ static void toss_rsb(struct kref *kref)
         rb_erase(&r->res_hashnode, &ls->ls_rsbtbl[r->res_bucket].keep);
         rsb_insert(r, &ls->ls_rsbtbl[r->res_bucket].toss);
         r->res_toss_time = jiffies;
+        ls->ls_rsbtbl[r->res_bucket].flags |= DLM_RTF_SHRINK;
         if (r->res_lvbptr) {
                 dlm_free_lvb(r->res_lvbptr);
                 r->res_lvbptr = NULL;
@@ -1659,11 +1660,18 @@ static void shrink_bucket(struct dlm_ls *ls, int b)
         char *name;
         int our_nodeid = dlm_our_nodeid();
         int remote_count = 0;
+        int need_shrink = 0;
         int i, len, rv;
 
         memset(&ls->ls_remove_lens, 0, sizeof(int) * DLM_REMOVE_NAMES_MAX);
 
         spin_lock(&ls->ls_rsbtbl[b].lock);
+
+        if (!(ls->ls_rsbtbl[b].flags & DLM_RTF_SHRINK)) {
+                spin_unlock(&ls->ls_rsbtbl[b].lock);
+                return;
+        }
+
         for (n = rb_first(&ls->ls_rsbtbl[b].toss); n; n = next) {
                 next = rb_next(n);
                 r = rb_entry(n, struct dlm_rsb, res_hashnode);
@@ -1679,6 +1687,8 @@ static void shrink_bucket(struct dlm_ls *ls, int b)
                         continue;
                 }
 
+                need_shrink = 1;
+
                 if (!time_after_eq(jiffies, r->res_toss_time +
                                    dlm_config.ci_toss_secs * HZ)) {
                         continue;
@@ -1710,6 +1720,11 @@ static void shrink_bucket(struct dlm_ls *ls, int b)
                 rb_erase(&r->res_hashnode, &ls->ls_rsbtbl[b].toss);
                 dlm_free_rsb(r);
         }
+
+        if (need_shrink)
+                ls->ls_rsbtbl[b].flags |= DLM_RTF_SHRINK;
+        else
+                ls->ls_rsbtbl[b].flags &= ~DLM_RTF_SHRINK;
         spin_unlock(&ls->ls_rsbtbl[b].lock);
 
         /*