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authorStefan Hajnoczi <stefanha@redhat.com>2014-07-07 15:15:52 +0200
committerKevin Wolf <kwolf@redhat.com>2014-08-15 15:07:14 +0200
commitac2662a913ee5854b1269256adbdc14e57ba480a (patch)
tree58946f4d817de43cbc5711b6c3b0095ef4f7dade
parent746ebfa77aa7a9550d11d3e7c8c10ecb8393ec76 (diff)
coroutine: make pool size dynamic
Allow coroutine users to adjust the pool size. For example, if the guest has multiple emulated disk drives we should keep around more coroutines. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
-rw-r--r--include/block/coroutine.h11
-rw-r--r--qemu-coroutine.c26
2 files changed, 34 insertions, 3 deletions
diff --git a/include/block/coroutine.h b/include/block/coroutine.h
index b408f96b82..b9b7f488c9 100644
--- a/include/block/coroutine.h
+++ b/include/block/coroutine.h
@@ -223,4 +223,15 @@ void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
* Note that this function clobbers the handlers for the file descriptor.
*/
void coroutine_fn yield_until_fd_readable(int fd);
+
+/**
+ * Add or subtract from the coroutine pool size
+ *
+ * The coroutine implementation keeps a pool of coroutines to be reused by
+ * qemu_coroutine_create(). This makes coroutine creation cheap. Heavy
+ * coroutine users should call this to reserve pool space. Call it again with
+ * a negative number to release pool space.
+ */
+void qemu_coroutine_adjust_pool_size(int n);
+
#endif /* QEMU_COROUTINE_H */
diff --git a/qemu-coroutine.c b/qemu-coroutine.c
index 470852100a..bd574aa1b5 100644
--- a/qemu-coroutine.c
+++ b/qemu-coroutine.c
@@ -19,14 +19,14 @@
#include "block/coroutine_int.h"
enum {
- /* Maximum free pool size prevents holding too many freed coroutines */
- POOL_MAX_SIZE = 64,
+ POOL_DEFAULT_SIZE = 64,
};
/** Free list to speed up creation */
static QemuMutex pool_lock;
static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
static unsigned int pool_size;
+static unsigned int pool_max_size = POOL_DEFAULT_SIZE;
Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
{
@@ -55,7 +55,7 @@ static void coroutine_delete(Coroutine *co)
{
if (CONFIG_COROUTINE_POOL) {
qemu_mutex_lock(&pool_lock);
- if (pool_size < POOL_MAX_SIZE) {
+ if (pool_size < pool_max_size) {
QSLIST_INSERT_HEAD(&pool, co, pool_next);
co->caller = NULL;
pool_size++;
@@ -137,3 +137,23 @@ void coroutine_fn qemu_coroutine_yield(void)
self->caller = NULL;
coroutine_swap(self, to);
}
+
+void qemu_coroutine_adjust_pool_size(int n)
+{
+ qemu_mutex_lock(&pool_lock);
+
+ pool_max_size += n;
+
+ /* Callers should never take away more than they added */
+ assert(pool_max_size >= POOL_DEFAULT_SIZE);
+
+ /* Trim oversized pool down to new max */
+ while (pool_size > pool_max_size) {
+ Coroutine *co = QSLIST_FIRST(&pool);
+ QSLIST_REMOVE_HEAD(&pool, pool_next);
+ pool_size--;
+ qemu_coroutine_delete(co);
+ }
+
+ qemu_mutex_unlock(&pool_lock);
+}