Implement talloc_pool()

A talloc pool is a chunk of memory that can be used as a context for further
talloc calls. Allocations with the pool as the parent just chew from that
memory by incrementing a pointer. If the talloc pool is full, then we fall back
to the normal system-level malloc(3) to get memory.

The use case for talloc pools is the transient memory that is used for handling
a single SMB request. Incrementing a pointer will be way faster than any malloc
implementation.

There is a downside of this: If you use talloc_steal() to move something out of
the pool, the whole pool memory is kept around until the last object inside the
pool is freed. So if you talloc_free() the pool, it might happen that the
memory is freed later. So don't hang anything off a talloc pool that should
live long.

Volker
(This used to be commit 60ef9a84f0bd18d48e453c08aa420d17275e0881)

1 files changed, 37 insertions, 0 deletions

diff --git a/source4/lib/talloc/testsuite.c b/source4/lib/talloc/testsuite.c
index e16c91f8b9..fedbda95aa 100644
--- a/source4/lib/talloc/testsuite.c
+++ b/source4/lib/talloc/testsuite.c
@@ -813,6 +813,25 @@ static bool test_speed(void)
 
 	talloc_free(ctx);
 
+	ctx = talloc_pool(NULL, 1024);
+
+	tv = timeval_current();
+	count = 0;
+	do {
+		void *p1, *p2, *p3;
+		for (i=0;i<loop;i++) {
+			p1 = talloc_size(ctx, loop % 100);
+			p2 = talloc_strdup(p1, "foo bar");
+			p3 = talloc_size(p1, 300);
+			talloc_free_children(ctx);
+		}
+		count += 3 * loop;
+	} while (timeval_elapsed(&tv) < 5.0);
+
+	talloc_free(ctx);
+
+	fprintf(stderr, "talloc_pool: %.0f ops/sec\n", count/timeval_elapsed(&tv));
+
 	tv = timeval_current();
 	count = 0;
 	do {
@@ -1066,6 +1085,23 @@ static bool test_autofree(void)
 	return true;
 }
 
+static bool test_pool(void)
+{
+	void *pool;
+	void *p1, *p2, *p3, *p4;
+
+	pool = talloc_pool(NULL, 1024);
+
+	p1 = talloc_size(pool, 80);
+	p2 = talloc_size(pool, 20);
+	p3 = talloc_size(p1, 50);
+	p4 = talloc_size(p3, 1000);
+
+	talloc_free(pool);
+
+	return true;
+}
+
 struct torture_context;
 bool torture_local_talloc(struct torture_context *tctx)
 {
@@ -1094,6 +1130,7 @@ bool torture_local_talloc(struct torture_context *tctx)
 	ret &= test_free_parent_deny_child(); 
 	ret &= test_talloc_ptrtype();
 	ret &= test_talloc_free_in_destructor();
+	ret &= test_pool();
 
 	if (ret) {
 		ret &= test_speed();