From 58e3931987377d3f4ec7bbc13e4ea0aab52dc6b0 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Wed, 4 Mar 2020 16:14:10 +0300 Subject: io-wq: optimise locking in io_worker_handle_work() There are 2 optimisations: - Now, io_worker_handler_work() do io_assign_current_work() twice per request, and each one adds lock/unlock(worker->lock) pair. The first is to reset worker->cur_work to NULL, and the second to set a real work shortly after. If there is a dependant work, set it immediately, that effectively removes the extra NULL'ing. - And there is no use in taking wqe->lock for linked works, as they are not hashed now. Optimise it out. Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe --- fs/io-wq.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'fs/io-wq.c') diff --git a/fs/io-wq.c b/fs/io-wq.c index e438dc4d7cb3..473af080470a 100644 --- a/fs/io-wq.c +++ b/fs/io-wq.c @@ -476,7 +476,7 @@ static void io_worker_handle_work(struct io_worker *worker) struct io_wq *wq = wqe->wq; do { - struct io_wq_work *work, *old_work; + struct io_wq_work *work; unsigned hash = -1U; /* @@ -495,12 +495,13 @@ static void io_worker_handle_work(struct io_worker *worker) spin_unlock_irq(&wqe->lock); if (!work) break; + io_assign_current_work(worker, work); /* handle a whole dependent link */ do { - io_assign_current_work(worker, work); - io_impersonate_work(worker, work); + struct io_wq_work *old_work; + io_impersonate_work(worker, work); /* * OK to set IO_WQ_WORK_CANCEL even for uncancellable * work, the worker function will do the right thing. @@ -513,10 +514,8 @@ static void io_worker_handle_work(struct io_worker *worker) old_work = work; work->func(&work); - - spin_lock_irq(&worker->lock); - worker->cur_work = NULL; - spin_unlock_irq(&worker->lock); + work = (old_work == work) ? NULL : work; + io_assign_current_work(worker, work); if (wq->put_work) wq->put_work(old_work); @@ -529,7 +528,7 @@ static void io_worker_handle_work(struct io_worker *worker) /* dependent work is not hashed */ hash = -1U; } - } while (work && work != old_work); + } while (work); spin_lock_irq(&wqe->lock); } while (1); -- cgit v1.2.3-59-g8ed1b