From fc666777da9da387354b1a142a6ffc5d43bc4f7e Mon Sep 17 00:00:00 2001 From: Jens Axboe <axboe@kernel.dk> Date: Wed, 19 Aug 2020 11:10:51 -0600 Subject: [PATCH] io_uring: use system_unbound_wq for ring exit work We currently use system_wq, which is unbounded in terms of number of workers. This means that if we're exiting tons of rings at the same time, then we'll briefly spawn tons of event kworkers just for a very short blocking time as the rings exit. Use system_unbound_wq instead, which has a sane cap on the concurrency level. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- fs/io_uring.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index e325895d681bf..1f2f31d93686f 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -7960,7 +7960,13 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx) ACCT_LOCKED); INIT_WORK(&ctx->exit_work, io_ring_exit_work); - queue_work(system_wq, &ctx->exit_work); + /* + * Use system_unbound_wq to avoid spawning tons of event kworkers + * if we're exiting a ton of rings at the same time. It just adds + * noise and overhead, there's no discernable change in runtime + * over using system_wq. + */ + queue_work(system_unbound_wq, &ctx->exit_work); } static int io_uring_release(struct inode *inode, struct file *file) -- GitLab