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[2003:dc:6f2b:6900:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38c2a1bb02dsm14160780f8f.70.2025.01.28.05.39.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jan 2025 05:39:40 -0800 (PST) From: Max Kellermann To: axboe@kernel.dk, asml.silence@gmail.com, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Max Kellermann Subject: [PATCH 5/8] io_uring/io-wq: do not use bogus hash value Date: Tue, 28 Jan 2025 14:39:24 +0100 Message-ID: <20250128133927.3989681-6-max.kellermann@ionos.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20250128133927.3989681-1-max.kellermann@ionos.com> References: <20250128133927.3989681-1-max.kellermann@ionos.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Previously, the `hash` variable was initialized with `-1` and only updated by io_get_next_work() if the current work was hashed. Commit 60cf46ae6054 ("io-wq: hash dependent work") changed this to always call io_get_work_hash() even if the work was not hashed. This caused the `hash != -1U` check to always be true, adding some overhead for the `hash->wait` code. This patch fixes the regression by checking the `IO_WQ_WORK_HASHED` flag. Perf diff for a flood of `IORING_OP_NOP` with `IOSQE_ASYNC`: 38.55% -1.57% [kernel.kallsyms] [k] queued_spin_lock_slowpath 6.86% -0.72% [kernel.kallsyms] [k] io_worker_handle_work 0.10% +0.67% [kernel.kallsyms] [k] put_prev_entity 1.96% +0.59% [kernel.kallsyms] [k] io_nop_prep 3.31% -0.51% [kernel.kallsyms] [k] try_to_wake_up 7.18% -0.47% [kernel.kallsyms] [k] io_wq_free_work Fixes: 60cf46ae6054 ("io-wq: hash dependent work") Cc: Pavel Begunkov Signed-off-by: Max Kellermann --- io_uring/io-wq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index ba9974e6f521..6e31f312b61a 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -604,7 +604,9 @@ static void io_worker_handle_work(struct io_wq_acct *acct, do { struct io_wq_work *next_hashed, *linked; unsigned int work_flags = atomic_read(&work->flags); - unsigned int hash = __io_get_work_hash(work_flags); + unsigned int hash = __io_wq_is_hashed(work_flags) + ? __io_get_work_hash(work_flags) + : -1U; next_hashed = wq_next_work(work); -- 2.45.2