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([2a01:e0a:1:6960:9f76:b012:ddc2:11de]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4247d0b63a9sm29408395e9.9.2024.06.20.08.22.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jun 2024 08:23:00 -0700 (PDT) Message-ID: Date: Thu, 20 Jun 2024 17:22:59 +0200 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/9] Add CPU-type to topology Content-Language: en-US To: Dave Hansen , srinivas pandruvada , Pawan Gupta Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, daniel.sneddon@linux.intel.com, tony.luck@intel.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-perf-users@vger.kernel.org, Josh Poimboeuf , "Rafael J. Wysocki" , Ricardo Neri , "Liang, Kan" , Andrew Cooper References: <20240617-add-cpu-type-v1-0-b88998c01e76@linux.intel.com> <8d757ea3-87a3-4663-ac76-66b04e33e6b3@gmail.com> <20240619015315.3ei5f6rovzdnxovo@desk> <0021f5f2-67c5-4b20-939d-48c9c1c60cdb@gmail.com> <1b99017a-6964-46de-ba3a-09552e7cf072@intel.com> From: Brice Goglin In-Reply-To: <1b99017a-6964-46de-ba3a-09552e7cf072@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 20/06/2024 à 17:06, Dave Hansen a écrit : > On 6/19/24 14:25, Brice Goglin wrote: >> Good point. From this patch series, I understand that the current kernel >> side doesn't care about these different E-cores. However it might be >> good to expose them as different cpu-types (or better name) to userspace ? >> >> Something like type 0 = P-core, 1 = normal E-core, 2 = low power E-core ? > The first priority here is getting the kernel to comprehend these types > for architectural purposes: when there are functional differences > between the cores. > > Let's get that in place, first. Then we can discuss the possibility of > new ABI in the area. Agreed. > Did the ARM folks ever do a sysfs ABI for big.LITTLE? I don't see > anything obvious in Documentation/ABI/testing/sysfs-devices-system-cpu. As far as I know, they only have the "capacity" field in sysfs cpu files that reports a higher number for the equivalent of P-core: From testing/sysfs-devices-system-cpu: What:           /sys/devices/system/cpu/cpuX/cpu_capacity Date:           December 2016 Contact:        Linux kernel mailing list Description:    information about CPUs heterogeneity.                 cpu_capacity: capacity of cpuX. I don't know how it's calculated but I've never seen it report something wrong. On Android/ARM phones, big cores usually have 1024 and small cores something between 400 and 500. Where there are 3 types of cores, they report 1024, 500-800 about ~250. Brice