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([2601:188:c180:4250:ecbe:130d:668d:951d]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4b3462c9646sm12961021cf.25.2025.09.02.07.28.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Sep 2025 07:28:59 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: Date: Tue, 2 Sep 2025 10:28:58 -0400 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 19/33] sched/isolation: Remove HK_TYPE_TICK test from cpu_is_isolated() To: Frederic Weisbecker , LKML Cc: Ingo Molnar , Marco Crivellari , Michal Hocko , Peter Zijlstra , Tejun Heo , Thomas Gleixner , Vlastimil Babka References: <20250829154814.47015-1-frederic@kernel.org> <20250829154814.47015-20-frederic@kernel.org> Content-Language: en-US In-Reply-To: <20250829154814.47015-20-frederic@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/29/25 11:48 AM, Frederic Weisbecker wrote: > It doesn't make sense to use nohz_full without also isolating the > related CPUs from the domain topology, either through the use of > isolcpus= or cpuset isolated partitions. > > And now HK_TYPE_DOMAIN includes all kinds of domain isolated CPUs. > > This means that HK_TYPE_KERNEL_NOISE (of which HK_TYPE_TICK is only an > alias) is always a superset of HK_TYPE_DOMAIN. That may not be true. Users can still set "isolcpus=" and "nohz_full=" with disjoint set of CPUs whether cpuset is used for additional isolated CPUs or not. Cheers, Longman > > Therefore if a CPU is not HK_TYPE_KERNEL_NOISE, it can't be > HK_TYPE_DOMAIN either. Testing the latter is then enough. > > Simplify cpu_is_isolated() accordingly. > > Signed-off-by: Frederic Weisbecker > --- > include/linux/sched/isolation.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h > index c02923ed4cbe..8d6d26d3fdf5 100644 > --- a/include/linux/sched/isolation.h > +++ b/include/linux/sched/isolation.h > @@ -82,8 +82,7 @@ static inline void housekeeping_init(void) { } > > static inline bool cpu_is_isolated(int cpu) > { > - return !housekeeping_test_cpu(cpu, HK_TYPE_DOMAIN) || > - !housekeeping_test_cpu(cpu, HK_TYPE_TICK); > + return !housekeeping_test_cpu(cpu, HK_TYPE_DOMAIN); > } > > #endif /* _LINUX_SCHED_ISOLATION_H */