From fe5c13ebf1161d0f324229cfb36cb5fb87ec6248 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Mon, 5 Dec 2011 19:20:12 +0200 Subject: [PATCH 22/25] 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 Signed-off-by: Kevin Wolf --- coroutine-ucontext.c | 30 ++++++++++++++++-------------- 1 files changed, 16 insertions(+), 14 deletions(-) diff --git a/coroutine-ucontext.c b/coroutine-ucontext.c index 2b8d3e9..3d01075 100644 --- a/coroutine-ucontext.c +++ b/coroutine-ucontext.c @@ -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; } -- 1.7.7.5