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[Qemu-devel] [PATCH 1/2] coroutine: make pool size dynamic
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 1/2] coroutine: make pool size dynamic |
Date: |
Thu, 3 Jul 2014 15:52:00 +0200 |
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 <address@hidden>
---
include/block/coroutine.h | 11 +++++++++++
qemu-coroutine.c | 25 +++++++++++++++++++------
2 files changed, 30 insertions(+), 6 deletions(-)
diff --git a/include/block/coroutine.h b/include/block/coroutine.h
index a1797ae..07eeb3c 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 4708521..d94234a 100644
--- a/qemu-coroutine.c
+++ b/qemu-coroutine.c
@@ -18,15 +18,11 @@
#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 QemuMutex pool_lock;
static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
static unsigned int pool_size;
+static unsigned int pool_max_size = 64;
Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
{
@@ -55,7 +51,7 @@ 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 +133,20 @@ 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;
+
+ /* 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);
+}
--
1.9.3