block: introduce aio task pool

Common interface for aio task loops. To be used for improving
performance of synchronous io loops in qcow2, block-stream,
copy-on-read, and may be other places.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190916175324.18478-3-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 124 insertions, 0 deletions

diff --git a/block/aio_task.c b/block/aio_task.c
new file mode 100644
index 0000000000..88989fa248
--- /dev/null
+++ b/block/aio_task.c
@@ -0,0 +1,124 @@
+/*
+ * Aio tasks loops
+ *
+ * Copyright (c) 2019 Virtuozzo International GmbH.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "block/aio.h"
+#include "block/aio_task.h"
+
+struct AioTaskPool {
+    Coroutine *main_co;
+    int status;
+    int max_busy_tasks;
+    int busy_tasks;
+    bool waiting;
+};
+
+static void coroutine_fn aio_task_co(void *opaque)
+{
+    AioTask *task = opaque;
+    AioTaskPool *pool = task->pool;
+
+    assert(pool->busy_tasks < pool->max_busy_tasks);
+    pool->busy_tasks++;
+
+    task->ret = task->func(task);
+
+    pool->busy_tasks--;
+
+    if (task->ret < 0 && pool->status == 0) {
+        pool->status = task->ret;
+    }
+
+    g_free(task);
+
+    if (pool->waiting) {
+        pool->waiting = false;
+        aio_co_wake(pool->main_co);
+    }
+}
+
+void coroutine_fn aio_task_pool_wait_one(AioTaskPool *pool)
+{
+    assert(pool->busy_tasks > 0);
+    assert(qemu_coroutine_self() == pool->main_co);
+
+    pool->waiting = true;
+    qemu_coroutine_yield();
+
+    assert(!pool->waiting);
+    assert(pool->busy_tasks < pool->max_busy_tasks);
+}
+
+void coroutine_fn aio_task_pool_wait_slot(AioTaskPool *pool)
+{
+    if (pool->busy_tasks < pool->max_busy_tasks) {
+        return;
+    }
+
+    aio_task_pool_wait_one(pool);
+}
+
+void coroutine_fn aio_task_pool_wait_all(AioTaskPool *pool)
+{
+    while (pool->busy_tasks > 0) {
+        aio_task_pool_wait_one(pool);
+    }
+}
+
+void coroutine_fn aio_task_pool_start_task(AioTaskPool *pool, AioTask *task)
+{
+    aio_task_pool_wait_slot(pool);
+
+    task->pool = pool;
+    qemu_coroutine_enter(qemu_coroutine_create(aio_task_co, task));
+}
+
+AioTaskPool *coroutine_fn aio_task_pool_new(int max_busy_tasks)
+{
+    AioTaskPool *pool = g_new0(AioTaskPool, 1);
+
+    pool->main_co = qemu_coroutine_self();
+    pool->max_busy_tasks = max_busy_tasks;
+
+    return pool;
+}
+
+void aio_task_pool_free(AioTaskPool *pool)
+{
+    g_free(pool);
+}
+
+int aio_task_pool_status(AioTaskPool *pool)
+{
+    if (!pool) {
+        return 0; /* Sugar for lazy allocation of aio pool */
+    }
+
+    return pool->status;
+}
+
+bool aio_task_pool_empty(AioTaskPool *pool)
+{
+    return pool->busy_tasks == 0;
+}