io_uring: batch completion in prior_task_list

In previous patches, we have already gathered some tw with
io_req_task_complete() as callback in prior_task_list, let's complete
them in batch while we cannot grab uring lock. In this way, we batch
the req_complete_post path.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20211208052125.351587-1-haoxu@linux.alibaba.com
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 21738ed..92dc335 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2225,7 +2225,49 @@ static void ctx_flush_and_put(struct io_ring_ctx *ctx, bool *locked)
        percpu_ref_put(&ctx->refs);
 }
 
-static void handle_tw_list(struct io_wq_work_node *node, struct io_ring_ctx **ctx, bool *locked)
+static inline void ctx_commit_and_unlock(struct io_ring_ctx *ctx)
+{
+       io_commit_cqring(ctx);
+       spin_unlock(&ctx->completion_lock);
+       io_cqring_ev_posted(ctx);
+}
+
+static void handle_prev_tw_list(struct io_wq_work_node *node,
+                               struct io_ring_ctx **ctx, bool *uring_locked)
+{
+       if (*ctx && !*uring_locked)
+               spin_lock(&(*ctx)->completion_lock);
+
+       do {
+               struct io_wq_work_node *next = node->next;
+               struct io_kiocb *req = container_of(node, struct io_kiocb,
+                                                   io_task_work.node);
+
+               if (req->ctx != *ctx) {
+                       if (unlikely(!*uring_locked && *ctx))
+                               ctx_commit_and_unlock(*ctx);
+
+                       ctx_flush_and_put(*ctx, uring_locked);
+                       *ctx = req->ctx;
+                       /* if not contended, grab and improve batching */
+                       *uring_locked = mutex_trylock(&(*ctx)->uring_lock);
+                       percpu_ref_get(&(*ctx)->refs);
+                       if (unlikely(!*uring_locked))
+                               spin_lock(&(*ctx)->completion_lock);
+               }
+               if (likely(*uring_locked))
+                       req->io_task_work.func(req, uring_locked);
+               else
+                       __io_req_complete_post(req, req->result, io_put_kbuf(req));
+               node = next;
+       } while (node);
+
+       if (unlikely(!*uring_locked))
+               ctx_commit_and_unlock(*ctx);
+}
+
+static void handle_tw_list(struct io_wq_work_node *node,
+                          struct io_ring_ctx **ctx, bool *locked)
 {
        do {
                struct io_wq_work_node *next = node->next;
@@ -2246,31 +2288,38 @@ static void handle_tw_list(struct io_wq_work_node *node, struct io_ring_ctx **ct
 
 static void tctx_task_work(struct callback_head *cb)
 {
-       bool locked = false;
+       bool uring_locked = false;
        struct io_ring_ctx *ctx = NULL;
        struct io_uring_task *tctx = container_of(cb, struct io_uring_task,
                                                  task_work);
 
        while (1) {
-               struct io_wq_work_node *node;
+               struct io_wq_work_node *node1, *node2;
 
-               if (!tctx->prior_task_list.first &&
-                   !tctx->task_list.first && locked)
+               if (!tctx->task_list.first &&
+                   !tctx->prior_task_list.first && uring_locked)
                        io_submit_flush_completions(ctx);
 
                spin_lock_irq(&tctx->task_lock);
-               node= wq_list_merge(&tctx->prior_task_list, &tctx->task_list);
-               if (!node)
+               node1 = tctx->prior_task_list.first;
+               node2 = tctx->task_list.first;
+               INIT_WQ_LIST(&tctx->task_list);
+               INIT_WQ_LIST(&tctx->prior_task_list);
+               if (!node2 && !node1)
                        tctx->task_running = false;
                spin_unlock_irq(&tctx->task_lock);
-               if (!node)
+               if (!node2 && !node1)
                        break;
 
-               handle_tw_list(node, &ctx, &locked);
+               if (node1)
+                       handle_prev_tw_list(node1, &ctx, &uring_locked);
+
+               if (node2)
+                       handle_tw_list(node2, &ctx, &uring_locked);
                cond_resched();
        }
 
-       ctx_flush_and_put(ctx, &locked);
+       ctx_flush_and_put(ctx, &uring_locked);
 }
 
 static void io_req_task_work_add(struct io_kiocb *req, bool priority)
@@ -2759,7 +2808,7 @@ static void io_complete_rw(struct kiocb *kiocb, long res)
                return;
        req->result = res;
        req->io_task_work.func = io_req_task_complete;
-       io_req_task_work_add(req, true);
+       io_req_task_work_add(req, !!(req->ctx->flags & IORING_SETUP_SQPOLL));
 }
 
 static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)