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[89.240.117.139]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c3e5389d57sm63078285a.64.2025.03.06.00.34.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Mar 2025 00:34:06 -0800 (PST) Date: Thu, 6 Mar 2025 08:34:02 +0000 From: Juri Lelli To: Shrikanth Hegde Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, hbathini@linux.ibm.com, joelagnelf@nvidia.com Subject: Re: [PATCH 2/2] sched/rt: update limit of sched_rt sysctl in documentation Message-ID: References: <20250306052954.452005-1-sshegde@linux.ibm.com> <20250306052954.452005-3-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: <20250306052954.452005-3-sshegde@linux.ibm.com> Hi, On 06/03/25 10:59, Shrikanth Hegde wrote: > By default fair_server dl_server allocates 5% of the bandwidth to the root > domain. Due to this writing any value less than 5% fails due to -EBUSY. > > cat /proc/sys/kernel/sched_rt_period_us > 1000000 > $ echo 49999 > /proc/sys/kernel/sched_rt_runtime_us > -bash: echo: write error: Device or resource busy > $ echo 50000 > /proc/sys/kernel/sched_rt_runtime_us > $ > > Since the sched_rt_runtime_us allows -1 as the minimum, put this > restriction in the documentation. > > One should check average of runtime/period in > /sys/kernel/debug/sched/fair_server/cpuX/* for exact value. > > Signed-off-by: Shrikanth Hegde > --- > Documentation/scheduler/sched-rt-group.rst | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/Documentation/scheduler/sched-rt-group.rst b/Documentation/scheduler/sched-rt-group.rst > index 80b05a3009ea..ab464335d320 100644 > --- a/Documentation/scheduler/sched-rt-group.rst > +++ b/Documentation/scheduler/sched-rt-group.rst > @@ -102,6 +102,9 @@ The system wide settings are configured under the /proc virtual file system: > * sched_rt_period_us takes values from 1 to INT_MAX. > * sched_rt_runtime_us takes values from -1 to sched_rt_period_us. > * A run time of -1 specifies runtime == period, ie. no limit. > + * sched_rt_runtime_us/sched_rt_period_us > 0.05 inorder to preserve > + bandwidth for fair dl_server. For accurate value check average of > + runtime/period in /sys/kernel/debug/sched/fair_server/cpuX/ Looks good to me. Reviewed-by: Juri Lelli Thanks! Juri