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[209.85.219.46]) by smtp.gmail.com with ESMTPSA id x7-20020ac84d47000000b003b2957fb45bsm551521qtv.8.2023.01.12.16.46.11 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Jan 2023 16:46:11 -0800 (PST) Received: by mail-qv1-f46.google.com with SMTP id d13so13832204qvj.8 for ; Thu, 12 Jan 2023 16:46:11 -0800 (PST) X-Received: by 2002:a0c:f38d:0:b0:534:252f:b091 with SMTP id i13-20020a0cf38d000000b00534252fb091mr369358qvk.130.1673570771350; Thu, 12 Jan 2023 16:46:11 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Thu, 12 Jan 2023 18:45:55 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: lockref scalability on x86-64 vs cpu_relax To: "Luck, Tony" Cc: Mateusz Guzik , linux-arch , Catalin Marinas , Will Deacon , Michael Ellerman , "linux-fsdevel@vger.kernel.org" , "viro@zeniv.linux.org.uk" , Jan Glauber , Linux ARM , linuxppc-dev X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230112_164616_637647_4F9D61E3 X-CRM114-Status: GOOD ( 10.97 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 12, 2023 at 6:31 PM Luck, Tony wrote: > > There's not much "simultaneous" in the SMT on ia64. Oh, I forgot about the whole SoEMT fiasco. Yeah, that might make ia64 act a bit differently here. But I don't think anybody cares any more, so I don't think that merits making this a per-architecture choice. The s390 people hated cpu_relax() here, but for them it was really because it was bad *everywhere*, and they just made it a no-op (see commit 22b6430d3665 "locking/core, s390: Make cpu_relax() a barrier again"). There had been a (failed) attempt at "cpu_relax_lowlatency()" for the s390 issues. Linus _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel