[PATCH 3/3] malloc_trim: clean up idle arenas immediately

[Eric Wong <e@80x24.org>]

There's no need to worry about race conditions if operating on
idle arenas, so clean them up immediately rather than cleaning
them up after a pthread_create (which may never come).

We'll also inform active threads about the trim earlier so they
have more cycles to react to the lazy trim request.
---
 mymalloc.h | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/mymalloc.h b/mymalloc.h
index e789cf3..4904b74 100644
--- a/mymalloc.h
+++ b/mymalloc.h
@@ -150,23 +150,30 @@ static void remote_free_finish(mstate ms)
 
 int malloc_trim(size_t pad)
 {
-	mstate ms = ms_tsd;
+	mstate m;
+	int ret = 0;
 
 	CHECK(int, 0, pthread_mutex_lock(&global_mtx));
-	{ /* be lazy for sibling threads, readers are not synchronized */
-		mstate m;
-		cds_list_for_each_entry(m, &arenas_unused, arena_node)
-			uatomic_set(&m->trim_check, 0);
-		cds_list_for_each_entry(m, &arenas_active, arena_node)
-			uatomic_set(&m->trim_check, 0);
+
+	/* be lazy for active sibling threads, readers are not synchronized */
+	cds_list_for_each_entry(m, &arenas_active, arena_node)
+		uatomic_set(&m->trim_check, 0);
+
+	/* nobody is using idle arenas, clean immediately */
+	cds_list_for_each_entry(m, &arenas_unused, arena_node) {
+		m->trim_check = 0;
+		remote_free_finish(m);
+		ret |= sys_trim(m, pad);
 	}
+
 	CHECK(int, 0, pthread_mutex_unlock(&global_mtx));
 
-	if (ms) { /* trim our own arena immediately */
-		remote_free_finish(ms);
-		return sys_trim(ms, pad);
+	m = ms_tsd;
+	if (m) { /* trim our own arena immediately */
+		remote_free_finish(m);
+		ret |= sys_trim(m, pad);
 	}
-	return 0;
+	return ret;
 }
 
 static void remote_free_enqueue(mstate fm, void *mem)