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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4836aa0847asm237182465e9.3.2026.02.14.03.31.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Feb 2026 03:31:24 -0800 (PST) Date: Sat, 14 Feb 2026 11:31:22 +0000 From: David Laight To: Ankur Arora Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, bpf@vger.kernel.org, arnd@arndb.de, catalin.marinas@arm.com, will@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, mark.rutland@arm.com, harisokn@amazon.com, cl@gentwo.org, ast@kernel.org, rafael@kernel.org, daniel.lezcano@linaro.org, memxor@gmail.com, zhenglifeng1@huawei.com, xueshuai@linux.alibaba.com, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com Subject: Re: [PATCH v9 01/12] asm-generic: barrier: Add smp_cond_load_relaxed_timeout() Message-ID: <20260214113122.70627a8b@pumpkin> In-Reply-To: <87tsvj6hwf.fsf@oracle.com> References: <20260209023153.2661784-1-ankur.a.arora@oracle.com> <20260209023153.2661784-2-ankur.a.arora@oracle.com> <20260212095621.4d99317b@pumpkin> <87tsvj6hwf.fsf@oracle.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260214_033128_206092_67C29334 X-CRM114-Status: GOOD ( 10.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 13 Feb 2026 20:58:08 -0800 Ankur Arora wrote: > David Laight writes: ... > > Plus the cost of evaluating cond_expr 200 times. > > I guess that isn't expected to contain a PCIe read :-) > > :). Good point. I'll see if I can add something like "when polling on > a memory address". I've only timed PCIe reads into an fpga (Cyclone V) target, but those are about 1 micro-second - which is a lot of clocks. Hard logic will be somewhat faster - but still slow. There might be other places where 200 isn't a good value. Perhaps add an extra #define that drops in the loop count? David