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Sat, 16 May 2026 21:19:52 -0700 (PDT) Date: Sun, 17 May 2026 05:19:50 +0100 From: Qais Yousef To: Ingo Molnar , Peter Zijlstra , Vincent Guittot Cc: Juri Lelli , Steven Rostedt , John Stultz , Thomas Gleixner , Frederic Weisbecker , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] sched/tick: Decouple sched_tick() from HZ Message-ID: <20260517041950.tqr27nax6e237roc@airbuntu> References: <20260517040740.444729-1-qyousef@layalina.io> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260517040740.444729-1-qyousef@layalina.io> On 05/17/26 05:07, Qais Yousef wrote: > Previous attempt to make HZ 1000 the default [1] to help with scheduler > responsiveness didn't get merged. But maybe for the best, as I think this idea > of decoupling sched_tick() from HZ makes more sense. We shouldn't need to make > a choice between how often timers should trigger vs how often should the > scheduler update its stats/take decisions. > > With HRTICK now is default on, preemption checks are less of problem. But tasks > could need to migrate (specifically on HMP systems) and frequencies could need > updating for solo long running tasks. > > The conversion is half complete. We need to invent a new jiffy (piffy?) and > move existing load balancing logic (and potentially other users if they want > to) to speed them up. BUT, with push load balancer patches circulating around, > I am not sure it is worth while or desired to speed it since we have a better > faster mechanism to keep the system balanced without the need for the 'heavy > handed' full load balance to trigger. The push lb can benefit from this ptick > too to ensure more responsiveness. Err, this whole series is RFC. Forgot to add the tag, sorry. > > [1] https://lore.kernel.org/lkml/20250226000810.459547-1-qyousef@layalina.io/ > > Qais Yousef (3): > sched/tick: Decouple sched_tick() from HZ > sched/tick: Move TICK_NSEC users to PTICK_NSEC > sched/tick: Turn on PTICK by default > > kernel/sched/clock.c | 4 +- > kernel/sched/core.c | 78 +++++++++++++++++++++++++++++--- > kernel/sched/cpufreq_schedutil.c | 2 +- > kernel/sched/fair.c | 6 +-- > kernel/sched/features.h | 8 ++++ > kernel/sched/sched.h | 7 +++ > 6 files changed, 93 insertions(+), 12 deletions(-) > > -- > 2.34.1 >