From af5d68f8892f8ee8f137648b79ceb2abc153a19b Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 2 Feb 2024 10:20:05 -0700 Subject: io_uring/sqpoll: manage task_work privately Decouple from task_work running, and cap the number of entries we process at the time. If we exceed that number, push remaining entries to a retry list that we'll process first next time. We cap the number of entries to process at 8, which is fairly random. We just want to get enough per-ctx batching here, while not processing endlessly. Since we manually run PF_IO_WORKER related task_work anyway as the task never exits to userspace, with this we no longer need to add an actual task_work item to the per-process list. Signed-off-by: Jens Axboe --- io_uring/io_uring.c | 46 ++++++++++++++++++++++++++++++++++++---------- io_uring/io_uring.h | 24 ++++++++++++++++++------ io_uring/sqpoll.c | 29 ++++++++++++++++++++++++++++- 3 files changed, 82 insertions(+), 17 deletions(-) (limited to 'io_uring') diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index bfd2f0fff153c..f1e3646c727c1 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1173,7 +1173,14 @@ static void ctx_flush_and_put(struct io_ring_ctx *ctx, struct io_tw_state *ts) percpu_ref_put(&ctx->refs); } -static void handle_tw_list(struct llist_node *node, unsigned int *count) +/* + * Run queued task_work, returning the number of entries processed in *count. + * If more entries than max_entries are available, stop processing once this + * is reached and return the rest of the list. + */ +struct llist_node *io_handle_tw_list(struct llist_node *node, + unsigned int *count, + unsigned int max_entries) { struct io_ring_ctx *ctx = NULL; struct io_tw_state ts = { }; @@ -1200,9 +1207,10 @@ static void handle_tw_list(struct llist_node *node, unsigned int *count) ctx = NULL; cond_resched(); } - } while (node); + } while (node && *count < max_entries); ctx_flush_and_put(ctx, &ts); + return node; } /** @@ -1247,27 +1255,41 @@ static __cold void io_fallback_tw(struct io_uring_task *tctx, bool sync) } } -void tctx_task_work(struct callback_head *cb) +struct llist_node *tctx_task_work_run(struct io_uring_task *tctx, + unsigned int max_entries, + unsigned int *count) { - struct io_uring_task *tctx = container_of(cb, struct io_uring_task, - task_work); struct llist_node *node; - unsigned int count = 0; if (unlikely(current->flags & PF_EXITING)) { io_fallback_tw(tctx, true); - return; + return NULL; } node = llist_del_all(&tctx->task_list); - if (node) - handle_tw_list(llist_reverse_order(node), &count); + if (node) { + node = llist_reverse_order(node); + node = io_handle_tw_list(node, count, max_entries); + } /* relaxed read is enough as only the task itself sets ->in_cancel */ if (unlikely(atomic_read(&tctx->in_cancel))) io_uring_drop_tctx_refs(current); - trace_io_uring_task_work_run(tctx, count); + trace_io_uring_task_work_run(tctx, *count); + return node; +} + +void tctx_task_work(struct callback_head *cb) +{ + struct io_uring_task *tctx; + struct llist_node *ret; + unsigned int count = 0; + + tctx = container_of(cb, struct io_uring_task, task_work); + ret = tctx_task_work_run(tctx, UINT_MAX, &count); + /* can't happen */ + WARN_ON_ONCE(ret); } static inline void io_req_local_work_add(struct io_kiocb *req, unsigned flags) @@ -1350,6 +1372,10 @@ static void io_req_normal_work_add(struct io_kiocb *req) if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) atomic_or(IORING_SQ_TASKRUN, &ctx->rings->sq_flags); + /* SQPOLL doesn't need the task_work added, it'll run it itself */ + if (ctx->flags & IORING_SETUP_SQPOLL) + return; + if (likely(!task_work_add(req->task, &tctx->task_work, ctx->notify_method))) return; diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h index 46795ee462dfb..38af827887860 100644 --- a/io_uring/io_uring.h +++ b/io_uring/io_uring.h @@ -57,6 +57,8 @@ void io_queue_iowq(struct io_kiocb *req, struct io_tw_state *ts_dont_use); void io_req_task_complete(struct io_kiocb *req, struct io_tw_state *ts); void io_req_task_queue_fail(struct io_kiocb *req, int ret); void io_req_task_submit(struct io_kiocb *req, struct io_tw_state *ts); +struct llist_node *io_handle_tw_list(struct llist_node *node, unsigned int *count, unsigned int max_entries); +struct llist_node *tctx_task_work_run(struct io_uring_task *tctx, unsigned int max_entries, unsigned int *count); void tctx_task_work(struct callback_head *cb); __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd); int io_uring_alloc_task_context(struct task_struct *task, @@ -275,6 +277,8 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx) static inline int io_run_task_work(void) { + bool ret = false; + /* * Always check-and-clear the task_work notification signal. With how * signaling works for task_work, we can find it set with nothing to @@ -286,18 +290,26 @@ static inline int io_run_task_work(void) * PF_IO_WORKER never returns to userspace, so check here if we have * notify work that needs processing. */ - if (current->flags & PF_IO_WORKER && - test_thread_flag(TIF_NOTIFY_RESUME)) { - __set_current_state(TASK_RUNNING); - resume_user_mode_work(NULL); + if (current->flags & PF_IO_WORKER) { + if (test_thread_flag(TIF_NOTIFY_RESUME)) { + __set_current_state(TASK_RUNNING); + resume_user_mode_work(NULL); + } + if (current->io_uring) { + unsigned int count = 0; + + tctx_task_work_run(current->io_uring, UINT_MAX, &count); + if (count) + ret = true; + } } if (task_work_pending(current)) { __set_current_state(TASK_RUNNING); task_work_run(); - return 1; + ret = true; } - return 0; + return ret; } static inline bool io_task_work_pending(struct io_ring_ctx *ctx) diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c index 65b5dbe3c850e..28bf0e085d310 100644 --- a/io_uring/sqpoll.c +++ b/io_uring/sqpoll.c @@ -18,6 +18,7 @@ #include "sqpoll.h" #define IORING_SQPOLL_CAP_ENTRIES_VALUE 8 +#define IORING_TW_CAP_ENTRIES_VALUE 8 enum { IO_SQ_THREAD_SHOULD_STOP = 0, @@ -219,8 +220,31 @@ static bool io_sqd_handle_event(struct io_sq_data *sqd) return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state); } +/* + * Run task_work, processing the retry_list first. The retry_list holds + * entries that we passed on in the previous run, if we had more task_work + * than we were asked to process. Newly queued task_work isn't run until the + * retry list has been fully processed. + */ +static unsigned int io_sq_tw(struct llist_node **retry_list, int max_entries) +{ + struct io_uring_task *tctx = current->io_uring; + unsigned int count = 0; + + if (*retry_list) { + *retry_list = io_handle_tw_list(*retry_list, &count, max_entries); + if (count >= max_entries) + return count; + max_entries -= count; + } + + *retry_list = tctx_task_work_run(tctx, max_entries, &count); + return count; +} + static int io_sq_thread(void *data) { + struct llist_node *retry_list = NULL; struct io_sq_data *sqd = data; struct io_ring_ctx *ctx; unsigned long timeout = 0; @@ -257,7 +281,7 @@ static int io_sq_thread(void *data) if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list))) sqt_spin = true; } - if (io_run_task_work()) + if (io_sq_tw(&retry_list, IORING_TW_CAP_ENTRIES_VALUE)) sqt_spin = true; if (sqt_spin || !time_after(jiffies, timeout)) { @@ -312,6 +336,9 @@ static int io_sq_thread(void *data) timeout = jiffies + sqd->sq_thread_idle; } + if (retry_list) + io_sq_tw(&retry_list, UINT_MAX); + io_uring_cancel_generic(true, sqd); sqd->thread = NULL; list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) -- cgit 1.2.3-korg