353 lines
9.4 KiB
C
353 lines
9.4 KiB
C
/*
|
|
* QEMU block layer thread pool
|
|
*
|
|
* Copyright IBM, Corp. 2008
|
|
* Copyright Red Hat, Inc. 2012
|
|
*
|
|
* Authors:
|
|
* Anthony Liguori <aliguori@us.ibm.com>
|
|
* Paolo Bonzini <pbonzini@redhat.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2. See
|
|
* the COPYING file in the top-level directory.
|
|
*
|
|
* Contributions after 2012-01-13 are licensed under the terms of the
|
|
* GNU GPL, version 2 or (at your option) any later version.
|
|
*/
|
|
#include "qemu/osdep.h"
|
|
#include "qemu/queue.h"
|
|
#include "qemu/thread.h"
|
|
#include "qemu/coroutine.h"
|
|
#include "trace.h"
|
|
#include "block/thread-pool.h"
|
|
#include "qemu/main-loop.h"
|
|
|
|
static void do_spawn_thread(ThreadPool *pool);
|
|
|
|
typedef struct ThreadPoolElement ThreadPoolElement;
|
|
|
|
enum ThreadState {
|
|
THREAD_QUEUED,
|
|
THREAD_ACTIVE,
|
|
THREAD_DONE,
|
|
};
|
|
|
|
struct ThreadPoolElement {
|
|
BlockAIOCB common;
|
|
ThreadPool *pool;
|
|
ThreadPoolFunc *func;
|
|
void *arg;
|
|
|
|
/* Moving state out of THREAD_QUEUED is protected by lock. After
|
|
* that, only the worker thread can write to it. Reads and writes
|
|
* of state and ret are ordered with memory barriers.
|
|
*/
|
|
enum ThreadState state;
|
|
int ret;
|
|
|
|
/* Access to this list is protected by lock. */
|
|
QTAILQ_ENTRY(ThreadPoolElement) reqs;
|
|
|
|
/* Access to this list is protected by the global mutex. */
|
|
QLIST_ENTRY(ThreadPoolElement) all;
|
|
};
|
|
|
|
struct ThreadPool {
|
|
AioContext *ctx;
|
|
QEMUBH *completion_bh;
|
|
QemuMutex lock;
|
|
QemuCond worker_stopped;
|
|
QemuSemaphore sem;
|
|
int max_threads;
|
|
QEMUBH *new_thread_bh;
|
|
|
|
/* The following variables are only accessed from one AioContext. */
|
|
QLIST_HEAD(, ThreadPoolElement) head;
|
|
|
|
/* The following variables are protected by lock. */
|
|
QTAILQ_HEAD(, ThreadPoolElement) request_list;
|
|
int cur_threads;
|
|
int idle_threads;
|
|
int new_threads; /* backlog of threads we need to create */
|
|
int pending_threads; /* threads created but not running yet */
|
|
bool stopping;
|
|
};
|
|
|
|
static void *worker_thread(void *opaque)
|
|
{
|
|
ThreadPool *pool = opaque;
|
|
|
|
qemu_mutex_lock(&pool->lock);
|
|
pool->pending_threads--;
|
|
do_spawn_thread(pool);
|
|
|
|
while (!pool->stopping) {
|
|
ThreadPoolElement *req;
|
|
int ret;
|
|
|
|
do {
|
|
pool->idle_threads++;
|
|
qemu_mutex_unlock(&pool->lock);
|
|
ret = qemu_sem_timedwait(&pool->sem, 10000);
|
|
qemu_mutex_lock(&pool->lock);
|
|
pool->idle_threads--;
|
|
} while (ret == -1 && !QTAILQ_EMPTY(&pool->request_list));
|
|
if (ret == -1 || pool->stopping) {
|
|
break;
|
|
}
|
|
|
|
req = QTAILQ_FIRST(&pool->request_list);
|
|
QTAILQ_REMOVE(&pool->request_list, req, reqs);
|
|
req->state = THREAD_ACTIVE;
|
|
qemu_mutex_unlock(&pool->lock);
|
|
|
|
ret = req->func(req->arg);
|
|
|
|
req->ret = ret;
|
|
/* Write ret before state. */
|
|
smp_wmb();
|
|
req->state = THREAD_DONE;
|
|
|
|
qemu_mutex_lock(&pool->lock);
|
|
|
|
qemu_bh_schedule(pool->completion_bh);
|
|
}
|
|
|
|
pool->cur_threads--;
|
|
qemu_cond_signal(&pool->worker_stopped);
|
|
qemu_mutex_unlock(&pool->lock);
|
|
return NULL;
|
|
}
|
|
|
|
static void do_spawn_thread(ThreadPool *pool)
|
|
{
|
|
QemuThread t;
|
|
|
|
/* Runs with lock taken. */
|
|
if (!pool->new_threads) {
|
|
return;
|
|
}
|
|
|
|
pool->new_threads--;
|
|
pool->pending_threads++;
|
|
|
|
qemu_thread_create(&t, "worker", worker_thread, pool, QEMU_THREAD_DETACHED);
|
|
}
|
|
|
|
static void spawn_thread_bh_fn(void *opaque)
|
|
{
|
|
ThreadPool *pool = opaque;
|
|
|
|
qemu_mutex_lock(&pool->lock);
|
|
do_spawn_thread(pool);
|
|
qemu_mutex_unlock(&pool->lock);
|
|
}
|
|
|
|
static void spawn_thread(ThreadPool *pool)
|
|
{
|
|
pool->cur_threads++;
|
|
pool->new_threads++;
|
|
/* If there are threads being created, they will spawn new workers, so
|
|
* we don't spend time creating many threads in a loop holding a mutex or
|
|
* starving the current vcpu.
|
|
*
|
|
* If there are no idle threads, ask the main thread to create one, so we
|
|
* inherit the correct affinity instead of the vcpu affinity.
|
|
*/
|
|
if (!pool->pending_threads) {
|
|
qemu_bh_schedule(pool->new_thread_bh);
|
|
}
|
|
}
|
|
|
|
static void thread_pool_completion_bh(void *opaque)
|
|
{
|
|
ThreadPool *pool = opaque;
|
|
ThreadPoolElement *elem, *next;
|
|
|
|
aio_context_acquire(pool->ctx);
|
|
restart:
|
|
QLIST_FOREACH_SAFE(elem, &pool->head, all, next) {
|
|
if (elem->state != THREAD_DONE) {
|
|
continue;
|
|
}
|
|
|
|
trace_thread_pool_complete(pool, elem, elem->common.opaque,
|
|
elem->ret);
|
|
QLIST_REMOVE(elem, all);
|
|
|
|
if (elem->common.cb) {
|
|
/* Read state before ret. */
|
|
smp_rmb();
|
|
|
|
/* Schedule ourselves in case elem->common.cb() calls aio_poll() to
|
|
* wait for another request that completed at the same time.
|
|
*/
|
|
qemu_bh_schedule(pool->completion_bh);
|
|
|
|
aio_context_release(pool->ctx);
|
|
elem->common.cb(elem->common.opaque, elem->ret);
|
|
aio_context_acquire(pool->ctx);
|
|
|
|
/* We can safely cancel the completion_bh here regardless of someone
|
|
* else having scheduled it meanwhile because we reenter the
|
|
* completion function anyway (goto restart).
|
|
*/
|
|
qemu_bh_cancel(pool->completion_bh);
|
|
|
|
qemu_aio_unref(elem);
|
|
goto restart;
|
|
} else {
|
|
qemu_aio_unref(elem);
|
|
}
|
|
}
|
|
aio_context_release(pool->ctx);
|
|
}
|
|
|
|
static void thread_pool_cancel(BlockAIOCB *acb)
|
|
{
|
|
ThreadPoolElement *elem = (ThreadPoolElement *)acb;
|
|
ThreadPool *pool = elem->pool;
|
|
|
|
trace_thread_pool_cancel(elem, elem->common.opaque);
|
|
|
|
QEMU_LOCK_GUARD(&pool->lock);
|
|
if (elem->state == THREAD_QUEUED &&
|
|
/* No thread has yet started working on elem. we can try to "steal"
|
|
* the item from the worker if we can get a signal from the
|
|
* semaphore. Because this is non-blocking, we can do it with
|
|
* the lock taken and ensure that elem will remain THREAD_QUEUED.
|
|
*/
|
|
qemu_sem_timedwait(&pool->sem, 0) == 0) {
|
|
QTAILQ_REMOVE(&pool->request_list, elem, reqs);
|
|
qemu_bh_schedule(pool->completion_bh);
|
|
|
|
elem->state = THREAD_DONE;
|
|
elem->ret = -ECANCELED;
|
|
}
|
|
|
|
}
|
|
|
|
static AioContext *thread_pool_get_aio_context(BlockAIOCB *acb)
|
|
{
|
|
ThreadPoolElement *elem = (ThreadPoolElement *)acb;
|
|
ThreadPool *pool = elem->pool;
|
|
return pool->ctx;
|
|
}
|
|
|
|
static const AIOCBInfo thread_pool_aiocb_info = {
|
|
.aiocb_size = sizeof(ThreadPoolElement),
|
|
.cancel_async = thread_pool_cancel,
|
|
.get_aio_context = thread_pool_get_aio_context,
|
|
};
|
|
|
|
BlockAIOCB *thread_pool_submit_aio(ThreadPool *pool,
|
|
ThreadPoolFunc *func, void *arg,
|
|
BlockCompletionFunc *cb, void *opaque)
|
|
{
|
|
ThreadPoolElement *req;
|
|
|
|
req = qemu_aio_get(&thread_pool_aiocb_info, NULL, cb, opaque);
|
|
req->func = func;
|
|
req->arg = arg;
|
|
req->state = THREAD_QUEUED;
|
|
req->pool = pool;
|
|
|
|
QLIST_INSERT_HEAD(&pool->head, req, all);
|
|
|
|
trace_thread_pool_submit(pool, req, arg);
|
|
|
|
qemu_mutex_lock(&pool->lock);
|
|
if (pool->idle_threads == 0 && pool->cur_threads < pool->max_threads) {
|
|
spawn_thread(pool);
|
|
}
|
|
QTAILQ_INSERT_TAIL(&pool->request_list, req, reqs);
|
|
qemu_mutex_unlock(&pool->lock);
|
|
qemu_sem_post(&pool->sem);
|
|
return &req->common;
|
|
}
|
|
|
|
typedef struct ThreadPoolCo {
|
|
Coroutine *co;
|
|
int ret;
|
|
} ThreadPoolCo;
|
|
|
|
static void thread_pool_co_cb(void *opaque, int ret)
|
|
{
|
|
ThreadPoolCo *co = opaque;
|
|
|
|
co->ret = ret;
|
|
aio_co_wake(co->co);
|
|
}
|
|
|
|
int coroutine_fn thread_pool_submit_co(ThreadPool *pool, ThreadPoolFunc *func,
|
|
void *arg)
|
|
{
|
|
ThreadPoolCo tpc = { .co = qemu_coroutine_self(), .ret = -EINPROGRESS };
|
|
assert(qemu_in_coroutine());
|
|
thread_pool_submit_aio(pool, func, arg, thread_pool_co_cb, &tpc);
|
|
qemu_coroutine_yield();
|
|
return tpc.ret;
|
|
}
|
|
|
|
void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg)
|
|
{
|
|
thread_pool_submit_aio(pool, func, arg, NULL, NULL);
|
|
}
|
|
|
|
static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
|
|
{
|
|
if (!ctx) {
|
|
ctx = qemu_get_aio_context();
|
|
}
|
|
|
|
memset(pool, 0, sizeof(*pool));
|
|
pool->ctx = ctx;
|
|
pool->completion_bh = aio_bh_new(ctx, thread_pool_completion_bh, pool);
|
|
qemu_mutex_init(&pool->lock);
|
|
qemu_cond_init(&pool->worker_stopped);
|
|
qemu_sem_init(&pool->sem, 0);
|
|
pool->max_threads = 64;
|
|
pool->new_thread_bh = aio_bh_new(ctx, spawn_thread_bh_fn, pool);
|
|
|
|
QLIST_INIT(&pool->head);
|
|
QTAILQ_INIT(&pool->request_list);
|
|
}
|
|
|
|
ThreadPool *thread_pool_new(AioContext *ctx)
|
|
{
|
|
ThreadPool *pool = g_new(ThreadPool, 1);
|
|
thread_pool_init_one(pool, ctx);
|
|
return pool;
|
|
}
|
|
|
|
void thread_pool_free(ThreadPool *pool)
|
|
{
|
|
if (!pool) {
|
|
return;
|
|
}
|
|
|
|
assert(QLIST_EMPTY(&pool->head));
|
|
|
|
qemu_mutex_lock(&pool->lock);
|
|
|
|
/* Stop new threads from spawning */
|
|
qemu_bh_delete(pool->new_thread_bh);
|
|
pool->cur_threads -= pool->new_threads;
|
|
pool->new_threads = 0;
|
|
|
|
/* Wait for worker threads to terminate */
|
|
pool->stopping = true;
|
|
while (pool->cur_threads > 0) {
|
|
qemu_sem_post(&pool->sem);
|
|
qemu_cond_wait(&pool->worker_stopped, &pool->lock);
|
|
}
|
|
|
|
qemu_mutex_unlock(&pool->lock);
|
|
|
|
qemu_bh_delete(pool->completion_bh);
|
|
qemu_sem_destroy(&pool->sem);
|
|
qemu_cond_destroy(&pool->worker_stopped);
|
|
qemu_mutex_destroy(&pool->lock);
|
|
g_free(pool);
|
|
}
|