coroutine: move pooling to common code

The coroutine pool code is duplicated between the ucontext and
sigaltstack backends, and absent from the win32 backend.  But the
code can be shared easily by moving it to qemu-coroutine.c.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 43 insertions, 2 deletions

diff --git a/qemu-coroutine.c b/qemu-coroutine.c
index 0f6e268574..25a14c605d 100644
--- a/qemu-coroutine.c
+++ b/qemu-coroutine.c
@@ -17,13 +17,54 @@
 #include "block/coroutine.h"
 #include "block/coroutine_int.h"
 
+enum {
+    /* Maximum free pool size prevents holding too many freed coroutines */
+    POOL_MAX_SIZE = 64,
+};
+
+/** Free list to speed up creation */
+static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
+static unsigned int pool_size;
+
 Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
 {
-    Coroutine *co = qemu_coroutine_new();
+    Coroutine *co;
+
+    co = QSLIST_FIRST(&pool);
+    if (co) {
+        QSLIST_REMOVE_HEAD(&pool, pool_next);
+        pool_size--;
+    } else {
+        co = qemu_coroutine_new();
+    }
+
     co->entry = entry;
     return co;
 }
 
+static void coroutine_delete(Coroutine *co)
+{
+    if (pool_size < POOL_MAX_SIZE) {
+        QSLIST_INSERT_HEAD(&pool, co, pool_next);
+        co->caller = NULL;
+        pool_size++;
+        return;
+    }
+
+    qemu_coroutine_delete(co);
+}
+
+static void __attribute__((destructor)) coroutine_cleanup(void)
+{
+    Coroutine *co;
+    Coroutine *tmp;
+
+    QSLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {
+        QSLIST_REMOVE_HEAD(&pool, pool_next);
+        qemu_coroutine_delete(co);
+    }
+}
+
 static void coroutine_swap(Coroutine *from, Coroutine *to)
 {
     CoroutineAction ret;
@@ -35,7 +76,7 @@ static void coroutine_swap(Coroutine *from, Coroutine *to)
         return;
     case COROUTINE_TERMINATE:
         trace_qemu_coroutine_terminate(to);
-        qemu_coroutine_delete(to);
+        coroutine_delete(to);
         return;
     default:
         abort();