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coroutine: make pool size dynamic

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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>
This commit is contained in:
Stefan Hajnoczi 2014-07-07 15:15:52 +02:00 committed by Kevin Wolf
parent 746ebfa77a
commit ac2662a913
2 changed files with 34 additions and 3 deletions
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11
include/block/coroutine.h
View File

@ -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 */

26
qemu-coroutine.c
View File

@ -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);
}