From 37f0e767e177af328fcaf74d3772495235e361a8 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Mon, 4 Oct 2021 20:02:53 +0100 Subject: [PATCH] io_uring: optimise ctx referencing by requests Currenlty, we allocate one ctx reference per request at submission time and put them at free. It's batched and not so expensive but it still bloats the kernel, adds 2 function calls for rcu and adds some overhead for request counting in io_free_batch_list(). Always keep one reference with a request, even when it's freed and in io_uring request caches. There is extra work at ring exit / quiesce paths, which now need to put all cached requests. io_ring_exit_work() is already looping, so it's not a problem. Add hybrid-busy waiting to io_ctx_quiesce() as well for now. Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/r/99613fbe396e80777228cde39bbda1aa8938554e.1633373302.git.asml.silence@gmail.com Signed-off-by: Jens Axboe --- fs/io_uring.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index c9e6f4b68718..9ec86e35668f 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1807,7 +1807,6 @@ static void io_req_complete_post(struct io_kiocb *req, long res, io_put_task(req->task, 1); wq_list_add_head(&req->comp_list, &ctx->locked_free_list); ctx->locked_free_nr++; - percpu_ref_put(&ctx->refs); } io_commit_cqring(ctx); spin_unlock(&ctx->completion_lock); @@ -1929,6 +1928,7 @@ static bool __io_alloc_req_refill(struct io_ring_ctx *ctx) ret = 1; } + percpu_ref_get_many(&ctx->refs, ret); for (i = 0; i < ret; i++) { req = reqs[i]; @@ -1986,8 +1986,6 @@ static void __io_free_req(struct io_kiocb *req) wq_list_add_head(&req->comp_list, &ctx->locked_free_list); ctx->locked_free_nr++; spin_unlock(&ctx->completion_lock); - - percpu_ref_put(&ctx->refs); } static inline void io_remove_next_linked(struct io_kiocb *req) @@ -2276,7 +2274,7 @@ static void io_free_batch_list(struct io_ring_ctx *ctx, __must_hold(&ctx->uring_lock) { struct task_struct *task = NULL; - int task_refs = 0, ctx_refs = 0; + int task_refs = 0; do { struct io_kiocb *req = container_of(node, struct io_kiocb, @@ -2296,12 +2294,9 @@ static void io_free_batch_list(struct io_ring_ctx *ctx, task_refs = 0; } task_refs++; - ctx_refs++; wq_stack_add_head(&req->comp_list, &ctx->submit_state.free_list); } while (node); - if (ctx_refs) - percpu_ref_put_many(&ctx->refs, ctx_refs); if (task) io_put_task(task, task_refs); } @@ -7212,8 +7207,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) return 0; /* make sure SQ entry isn't read before tail */ nr = min3(nr, ctx->sq_entries, entries); - if (unlikely(!percpu_ref_tryget_many(&ctx->refs, nr))) - return -EAGAIN; io_get_task_refs(nr); io_submit_state_start(&ctx->submit_state, nr); @@ -7243,7 +7236,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) int unused = nr - ref_used; current->io_uring->cached_refs += unused; - percpu_ref_put_many(&ctx->refs, unused); } io_submit_state_end(ctx); @@ -9164,6 +9156,7 @@ static void io_destroy_buffers(struct io_ring_ctx *ctx) static void io_req_caches_free(struct io_ring_ctx *ctx) { struct io_submit_state *state = &ctx->submit_state; + int nr = 0; mutex_lock(&ctx->uring_lock); io_flush_cached_locked_reqs(ctx, state); @@ -9175,7 +9168,10 @@ static void io_req_caches_free(struct io_ring_ctx *ctx) node = wq_stack_extract(&state->free_list); req = container_of(node, struct io_kiocb, comp_list); kmem_cache_free(req_cachep, req); + nr++; } + if (nr) + percpu_ref_put_many(&ctx->refs, nr); mutex_unlock(&ctx->uring_lock); } @@ -9345,6 +9341,8 @@ static void io_ring_exit_work(struct work_struct *work) io_sq_thread_unpark(sqd); } + io_req_caches_free(ctx); + if (WARN_ON_ONCE(time_after(jiffies, timeout))) { /* there is little hope left, don't run it too often */ interval = HZ * 60; @@ -10724,10 +10722,14 @@ static int io_ctx_quiesce(struct io_ring_ctx *ctx) */ mutex_unlock(&ctx->uring_lock); do { - ret = wait_for_completion_interruptible(&ctx->ref_comp); - if (!ret) + ret = wait_for_completion_interruptible_timeout(&ctx->ref_comp, HZ); + if (ret) { + ret = min(0L, ret); break; + } + ret = io_run_task_work_sig(); + io_req_caches_free(ctx); } while (ret >= 0); mutex_lock(&ctx->uring_lock); -- 2.25.1