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[195.38.112.2]) by smtp.gmail.com with ESMTPSA id kg26-20020a17090776fa00b00a449026672esm545578ejc.81.2024.03.28.02.43.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Mar 2024 02:43:56 -0700 (PDT) Sender: Ingo Molnar Date: Thu, 28 Mar 2024 10:43:54 +0100 From: Ingo Molnar To: Vincent Guittot Cc: Shrikanth Hegde , peterz@infradead.org, dietmar.eggemann@arm.com, qyousef@layalina.io, linux-kernel@vger.kernel.org, vschneid@redhat.com Subject: Re: [PATCH] sched/fair: Combine EAS check with overutilized access Message-ID: References: <20240326152616.380999-1-sshegde@linux.ibm.com> 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=us-ascii Content-Disposition: inline In-Reply-To: * Vincent Guittot wrote: > On Tue, 26 Mar 2024 at 20:32, Ingo Molnar wrote: > > > > > > * Shrikanth Hegde wrote: > > > > > Access to overutilized is always used with sched_energy_enabled in > > > the pattern: > > > > > > if (sched_energy_enabled && !overutilized) > > > do something > > > > > > So modify the helper function to return this pattern. This is more > > > readable code as it would say, do something when root domain is not > > > overutilized. This function always return true when EAS is disabled. > > > > > > No change in functionality intended. > > > > > > Suggested-by: Vincent Guittot > > > Signed-off-by: Shrikanth Hegde > > > --- > > > kernel/sched/fair.c | 20 +++++++------------- > > > 1 file changed, 7 insertions(+), 13 deletions(-) > > > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > > index 24a7530a7d3f..e222e3ad4cfe 100644 > > > --- a/kernel/sched/fair.c > > > +++ b/kernel/sched/fair.c > > > @@ -6686,12 +6686,11 @@ static inline bool cpu_overutilized(int cpu) > > > } > > > > > > /* > > > - * Ensure that caller can do EAS. overutilized value > > > - * make sense only if EAS is enabled > > > + * overutilized value make sense only if EAS is enabled > > > */ > > > static inline int is_rd_overutilized(struct root_domain *rd) > > > { > > > - return READ_ONCE(rd->overutilized); > > > + return !sched_energy_enabled() || READ_ONCE(rd->overutilized); > > > } > > > > > > static inline void set_rd_overutilized_status(struct root_domain *rd, > > > @@ -6710,8 +6709,6 @@ static inline void check_update_overutilized_status(struct rq *rq) > > > * overutilized field is used for load balancing decisions only > > > * if energy aware scheduler is being used > > > */ > > > - if (!sched_energy_enabled()) > > > - return; > > > > > > if (!is_rd_overutilized(rq->rd) && cpu_overutilized(rq->cpu)) > > > set_rd_overutilized_status(rq->rd, SG_OVERUTILIZED); > > > > On a second thought, I'm not sure removing the open-coded > > sched_energy_enabled() branches is a good idea: the current code makes it > > really, really clear when we are within EAS code paths. > > > > Hiding it within is_rd_overutilized() makes it a lot less obvious IMO. > > That's probably a matter of pov. I prefer embedding everything to make > sure to have useless access to rd->overutilized Ok, fair enough - applied to tip:sched/core, thanks guys! Ingo