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Wed, 21 Oct 2026 05:44:25 -0700 (PDT) Received: from scheduler.schedules ([85.100.66.184]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e254ef1bfsm5587546f8f.6.2026.10.21.05.44.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 05:44:24 -0700 (PDT) Date: Wed, 21 Oct 2026 15:44:21 +0300 From: Kayra Cizmeci To: Li kunyu Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/6] sched/fair: Introduce the SMT_BUDDY_ASSIST feature Message-ID: References: <20261020083746.37068-1-likunyu@open-hieco.net> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261020083746.37068-1-likunyu@open-hieco.net> On Tue, Oct 20, 2026 at 04:37:40PM +0800, Li kunyu wrote: > Several benchmarks show performance regressions: > > 1. tbench 32 8325.17 6772.693 -18.65%(degeneration): > Each tbench sample was run three times. Initially, some measurement > error was observed. Moreover, this patch series essentially utilized all > idle CPUs, whereas without the feature enabled, 5% to 10% of idle CPUs may > remain idle. This led to more CPUs experiencing cache interference and > other effects. The results are benign and within an acceptable range. According to what the results are 'acceptable'? If there were some error why even talk about them? > > 2. schbench(99th) 8 13.8 15.0 -8.70%(degeneration): > The situation is similar to that observed with tbench. Each sample was > tested five times. The primary regression occurs under bursty task > scenarios, in which tasks are spread across idle CPUs, resulting in > increased memory bandwidth contention, cache latency, and other delays > over a short interval. This is also considered acceptable. > > > Li kunyu (6): > sched/fair: Add SMT sibling push in periodic load balance > sched/fair: Add is_smt_buddy_run() to skip SMT domain > sched/fair: SMT sibling exclusion after successful push > sched/fair: Restrict newidle balance to LLC domain > sched/fair: Add task burst threshold for large-scale bursts > sched/docs: Add documentation for SMT Buddy Assist feature > > Documentation/scheduler/smt-buddy-assist.rst | 126 ++++++++++ > kernel/sched/fair.c | 239 ++++++++++++++++++- > kernel/sched/features.h | 9 + > 3 files changed, 364 insertions(+), 10 deletions(-) > create mode 100644 Documentation/scheduler/smt-buddy-assist.rst > > -- > 2.47.3 >