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coroutine: switch per-thread free pool to a global pool 

ucontext-based coroutines use a free pool to reduce allocations and
deallocations of coroutine objects.  The pool is per-thread, presumably
to improve locality.  However, as coroutines are usually allocated in
a vcpu thread and freed in the I/O thread, the pool accounting gets
screwed up and we end allocating and freeing a coroutine for every I/O
request.  This is expensive since large objects are allocated via the
kernel, and are not cached by the C runtime.

Fix by switching to a global pool.  This is safe since we're protected
by the global mutex.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Avi Kivity 2011-12-05 19:20:12 +02:00 committed by Kevin Wolf
parent c2c9a46609
commit 39a7a362e1
1 changed files with 16 additions and 14 deletions
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30
coroutine-ucontext.c
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@ -35,6 +35,10 @@ enum {
POOL_MAX_SIZE = 64,
};
/** Free list to speed up creation */
static QLIST_HEAD(, Coroutine) pool = QLIST_HEAD_INITIALIZER(pool);
static unsigned int pool_size;
typedef struct {
Coroutine base;
void *stack;
@ -48,10 +52,6 @@ typedef struct {
/** Currently executing coroutine */
Coroutine *current;
/** Free list to speed up creation */
QLIST_HEAD(, Coroutine) pool;
unsigned int pool_size;
/** The default coroutine */
CoroutineUContext leader;
} CoroutineThreadState;
@ -75,7 +75,6 @@ static CoroutineThreadState *coroutine_get_thread_state(void)
if (!s) {
s = g_malloc0(sizeof(*s));
s->current = &s->leader.base;
QLIST_INIT(&s->pool);
pthread_setspecific(thread_state_key, s);
}
return s;
@ -84,14 +83,19 @@ static CoroutineThreadState *coroutine_get_thread_state(void)
static void qemu_coroutine_thread_cleanup(void *opaque)
{
CoroutineThreadState *s = opaque;
g_free(s);
}
static void __attribute__((destructor)) coroutine_cleanup(void)
{
Coroutine *co;
Coroutine *tmp;
QLIST_FOREACH_SAFE(co, &s->pool, pool_next, tmp) {
QLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {
g_free(DO_UPCAST(CoroutineUContext, base, co)->stack);
g_free(co);
}
g_free(s);
}
static void __attribute__((constructor)) coroutine_init(void)
@ -169,13 +173,12 @@ static Coroutine *coroutine_new(void)
Coroutine *qemu_coroutine_new(void)
{
CoroutineThreadState *s = coroutine_get_thread_state();
Coroutine *co;
co = QLIST_FIRST(&s->pool);
co = QLIST_FIRST(&pool);
if (co) {
QLIST_REMOVE(co, pool_next);
s->pool_size--;
pool_size--;
} else {
co = coroutine_new();
}
@ -184,13 +187,12 @@ Coroutine *qemu_coroutine_new(void)
void qemu_coroutine_delete(Coroutine *co_)
{
CoroutineThreadState *s = coroutine_get_thread_state();
CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
if (s->pool_size < POOL_MAX_SIZE) {
QLIST_INSERT_HEAD(&s->pool, &co->base, pool_next);
if (pool_size < POOL_MAX_SIZE) {
QLIST_INSERT_HEAD(&pool, &co->base, pool_next);
co->base.caller = NULL;
s->pool_size++;
pool_size++;
return;
}