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Wed, 29 Apr 2026 01:51:55 -0700 (PDT) From: Qing Wang To: peterz@infradead.org Cc: abuehaze@amazon.com, adamli@os.amperecomputing.com, bsegall@google.com, clm@meta.com, dietmar.eggemann@arm.com, joseph.salisbury@oracle.com, joshdon@google.com, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, mgorman@suse.de, mingo@redhat.com, rostedt@goodmis.org, vincent.guittot@linaro.org, vschneid@redhat.com Subject: Re: [PATCH 4/4] sched/fair: Proportional newidle balance Date: Wed, 29 Apr 2026 16:51:47 +0800 Message-Id: <20260429085147.1029505-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251107161739.770122091@infradead.org> References: <20251107161739.770122091@infradead.org> 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-Transfer-Encoding: 8bit On Sat, 08 Nov 2025 at 00:06, Peter Zijlstra wrote: > if (sd->flags & SD_BALANCE_NEWIDLE) { > + unsigned int weight = 1; > + > + if (sched_feat(NI_RANDOM)) { > + /* > + * Throw a 1k sided dice; and only run > + * newidle_balance according to the success > + * rate. > + */ > + u32 d1k = sched_rng() % 1024; > + weight = 1 + sd->newidle_ratio; > + if (d1k > weight) { > + update_newidle_stats(sd, 0); > + continue; > + } > + weight = (1024 + weight/2) / weight; > + } Hi Peter, I think this optimization approach is excellent. However, there is a small idea for discussion: would using a count-based window (e.g., if the current success rate is 50%, then within every window of 100 attempts, exactly 50 are allowed to do balancing) be more stable than using a random number to trigger balancing? This is just an idea for discussion. I haven’t implemented and validated it yet -- Best regards, Qing