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([2601:188:c102:b180:1f8b:71d0:77b1:1f6e]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c37f4a6441sm1556650385a.7.2026.01.12.08.02.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Jan 2026 08:02:30 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <86b578f3-70f5-4a72-9371-e35478ec1c01@redhat.com> Date: Mon, 12 Jan 2026 11:02:28 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH cgroup/for-6.20 v4 4/5] cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict To: Waiman Long , =?UTF-8?Q?Michal_Koutn=C3=BD?= Cc: Tejun Heo , Johannes Weiner , Jonathan Corbet , Shuah Khan , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, Sun Shaojie , Chen Ridong , Chen Ridong References: <20260112040856.460904-1-longman@redhat.com> <20260112040856.460904-5-longman@redhat.com> <2naek52bbrod4wf5dbyq2s3odqswy2urrwzsqxv3ozrtugioaw@sjw5m6gizl33> <9a1b7583-7695-484f-a290-807b6db06799@redhat.com> Content-Language: en-US In-Reply-To: <9a1b7583-7695-484f-a290-807b6db06799@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 1/12/26 10:15 AM, Waiman Long wrote: > On 1/12/26 10:08 AM, Michal Koutný wrote: >> On Mon, Jan 12, 2026 at 09:51:28AM -0500, Waiman Long >> wrote: >>> Sorry, I might have missed this comment of yours. The >>> "cpuset.cpus.exclusive" file lists all the CPUs that can be granted >>> to its >>> children as exclusive CPUs. The cgroup root is an implicit partition >>> root >>> where all its CPUs can be granted to its children whether they are >>> online or >>> offline. "cpuset.cpus.effective" OTOH ignores the offline CPUs as >>> well as >>> exclusive CPUs that have been passed down to existing descendant >>> partition >>> roots so it may differ from the implicit "cpuset.cpus.exclusive". >> Howewer, there's no "cpuset.cpus" configurable nor visible on the root >> cgroup. So possibly drop this hunk altogether for simplicity? > > Ah, you are right. I thought there was a read-only copy in cgroup > root. Will correct that. > Below is the doc diff between v4 and v5: diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index a3446db96cea..28613c0e1c90 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -2641,9 +2641,10 @@ Cpuset Interface Files      The root cgroup is always a partition root and its state cannot      be changed.  All other non-root cgroups start out as "member". -    Even though the "cpuset.cpus.exclusive*" control files are not -    present in the root cgroup, they are implicitly the same as -    "cpuset.cpus". +    Even though the "cpuset.cpus.exclusive*" and "cpuset.cpus" +    control files are not present in the root cgroup, they are +    implicitly the same as the "/sys/devices/system/cpu/possible" +    sysfs file.      When set to "root", the current cgroup is the root of a new      partition or scheduling domain.  The set of exclusive CPUs is Cheers, Longman