[PATCH 6/6] io_uring: batch completion in prior_task_list

Hao Xu
2021-10-29T12:22:51Z

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 regardless uring lock. For instance, we are doing simple
direct read, most task work will be io_req_task_complete(), with this
patch we don't need to hold uring lock there for long time.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
---
fs/io_uring.c | 52 ++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 43 insertions(+), 9 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 694195c086f3..565cd0b34f18 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2166,6 +2166,37 @@ static inline unsigned int io_put_rw_kbuf(struct io_kiocb *req)
return io_put_kbuf(req, req->kbuf);
}

+static void handle_prior_tw_list(struct io_wq_work_node *node)
+{
+ struct io_ring_ctx *ctx = NULL;
+
+ 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 (ctx) {
+ io_commit_cqring(ctx);
+ spin_unlock(&ctx->completion_lock);
+ io_cqring_ev_posted(ctx);
+ percpu_ref_put(&ctx->refs);
+ }
+ ctx = req->ctx;
+ percpu_ref_get(&ctx->refs);
+ spin_lock(&ctx->completion_lock);
+ }
+ __io_req_complete_post(req, req->result, io_put_rw_kbuf(req));
+ node = next;
+ } while (node);
+
+ if (ctx) {
+ io_commit_cqring(ctx);
+ spin_unlock(&ctx->completion_lock);
+ io_cqring_ev_posted(ctx);
+ percpu_ref_put(&ctx->refs);
+ }
+}
+
static void handle_tw_list(struct io_wq_work_node *node, struct io_ring_ctx **ctx, bool *locked)
{
do {
@@ -2193,25 +2224,28 @@ static void tctx_task_work(struct callback_head *cb)
task_work);

while (1) {
- struct io_wq_work_node *node;
- struct io_wq_work_list *merged_list;
+ 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 && locked)
io_submit_flush_completions(ctx);

spin_lock_irq(&tctx->task_lock);
- merged_list = wq_list_merge(&tctx->prior_task_list, &tctx->task_list);
- node = merged_list->first;
+ 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 (!node)
+ 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_prior_tw_list(node1);
+
+ if (node2)
+ handle_tw_list(node2, &ctx, &locked);
cond_resched();
}

--
2.24.4