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Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Guenter Roeck , Frederic Weisbecker , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Anna-Maria Behnsen , Ingo Molnar , Chen Ridong , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-hyperv@vger.kernel.org, linux-hwmon@vger.kernel.org, rcu@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Costa Shulyupin , Qiliang Yuan References: <20260421030351.281436-1-longman@redhat.com> <20260421030351.281436-4-longman@redhat.com> <875x5kd88d.ffs@tglx> Content-Language: en-US From: Waiman Long In-Reply-To: <875x5kd88d.ffs@tglx> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On 4/21/26 4:32 AM, Thomas Gleixner wrote: > On Mon, Apr 20 2026 at 23:03, Waiman Long wrote: >> To provide nohz_full tick support, there is a set of tick dependency >> masks that need to be evaluated on every IRQ and context switch. > s/IRQ/interrupt/ > > This is a changelog and not a SMS service. >> Switching on nohz_full tick support at runtime will be problematic >> as some of the tick dependency masks may not be properly set causing >> problem down the road. > That's useless blurb with zero content. > >> Allow nohz_full boot option to be specified without any >> parameter to force enable nohz_full tick support without any >> CPU in the tick_nohz_full_mask yet. The context_tracking_key and >> tick_nohz_full_running flag will be enabled in this case to make >> tick_nohz_full_enabled() return true. > I kinda can crystal-ball what you are trying to say here, but that does > not make it qualified as a proper change log. > >> There is still a small performance overhead by force enable nohz_full >> this way. So it should only be used if there is a chance that some >> CPUs may become isolated later via the cpuset isolated partition >> functionality and better CPU isolation closed to nohz_full is desired. > Why has this key to be enabled on boot if there are no CPUs in the > isolated mask? > > If you want to manage this dynamically at runtime then enable the key > once CPUs are isolated. Yes, it's more work, but that avoids the "should > only be used" nonsense and makes this more robust down the road. OK, I will try to make it fully dynamic. Of course, it will be more work. Cheers, Longman > Thanks, > > tglx > >