pruning buffer margin - do not destroy if no other non-filled arenas are in the pool

2 files changed, 26 insertions, 3 deletions

diff --git a/libglusterfs/src/iobuf.c b/libglusterfs/src/iobuf.c
index 84e3b5efec6..7cbc1702e7e 100644
--- a/libglusterfs/src/iobuf.c
+++ b/libglusterfs/src/iobuf.c
@@ -144,11 +144,30 @@ err:
 
 
 struct iobuf_arena *
+__iobuf_arena_unprune (struct iobuf_pool *iobuf_pool)
+{
+        struct iobuf_arena *iobuf_arena = NULL;
+        struct iobuf_arena *tmp = NULL;
+
+        list_for_each_entry (tmp, &iobuf_pool->purge.list, list) {
+                list_del_init (&tmp->list);
+                iobuf_arena = tmp;
+                break;
+        }
+
+        return iobuf_arena;
+}
+
+
+struct iobuf_arena *
 __iobuf_pool_add_arena (struct iobuf_pool *iobuf_pool)
 {
         struct iobuf_arena *iobuf_arena = NULL;
 
-        iobuf_arena = __iobuf_arena_alloc (iobuf_pool);
+        iobuf_arena = __iobuf_arena_unprune (iobuf_pool);
+
+        if (!iobuf_arena)
+                iobuf_arena = __iobuf_arena_alloc (iobuf_pool);
 
         if (!iobuf_arena)
                 return NULL;
@@ -221,13 +240,17 @@ iobuf_pool_new (size_t arena_size, size_t page_size)
 }
 
 
-
 void
 __iobuf_pool_prune (struct iobuf_pool *iobuf_pool)
 {
         struct iobuf_arena *iobuf_arena = NULL;
         struct iobuf_arena *tmp = NULL;
 
+        if (list_empty (&iobuf_pool->arenas.list))
+                /* buffering - preserve this one arena (if at all)
+                   for __iobuf_arena_unprune */
+                return;
+
         list_for_each_entry_safe (iobuf_arena, tmp, &iobuf_pool->purge.list,
                                   list) {
                 if (iobuf_arena->active_cnt)
diff --git a/libglusterfs/src/iobuf.h b/libglusterfs/src/iobuf.h
index 4c34770849e..71b115c5d40 100644
--- a/libglusterfs/src/iobuf.h
+++ b/libglusterfs/src/iobuf.h
@@ -86,7 +86,7 @@ struct iobuf_pool {
         struct iobuf_arena  arenas;     /* head node arena
                                            (unused by itself) */
         struct iobuf_arena  filled;     /* arenas without  free iobufs */
-        struct iobuf_arena  purge;      /* arenas to be purged right away */
+        struct iobuf_arena  purge;      /* arenas which can be purged */
 };