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Wysocki" , Peter Zijlstra , Christian Loehle , Frederic Weisbecker Subject: [PATCH] Documentation: sched/RT: Update paragraphs about RT bandwidth control Date: Wed, 11 Dec 2024 18:00:52 +0100 Message-ID: <20241211170052.2449581-1-mkoutny@suse.com> X-Mailer: git-send-email 2.47.0 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: quoted-printable This has slightly changed with the introduction of fair_server. Update the most relevant parts. Link: https://lore.kernel.org/r/Z0c8S8i3qt7SEU14@jlelli-thinkpadt14gen4.rem= ote.csb/ Signed-off-by: Michal Koutn=C3=BD Reviewed-by: Juri Lelli --- Documentation/scheduler/sched-deadline.rst | 13 +++++++------ Documentation/scheduler/sched-rt-group.rst | 8 ++++---- 2 files changed, 11 insertions(+), 10 deletions(-) diff --git a/Documentation/scheduler/sched-deadline.rst b/Documentation/sch= eduler/sched-deadline.rst index 22838ed8e13aa..a727827b8dd52 100644 --- a/Documentation/scheduler/sched-deadline.rst +++ b/Documentation/scheduler/sched-deadline.rst @@ -591,12 +591,13 @@ Deadline Task Scheduling =20 The system wide settings are configured under the /proc virtual file syst= em. =20 - For now the -rt knobs are used for -deadline admission control and the - -deadline runtime is accounted against the -rt runtime. We realize that t= his - isn't entirely desirable; however, it is better to have a small interface= for - now, and be able to change it easily later. The ideal situation (see 5.) = is to - run -rt tasks from a -deadline server; in which case the -rt bandwidth is= a - direct subset of dl_bw. + For now the -rt knobs are used for -deadline admission control and with + CONFIG_RT_GROUP_SCHED the -deadline runtime is accounted against the (roo= t) + -rt runtime. With !CONFIG_RT_GROUP_SCHED the knob only serves for the -dl + admission control. We realize that this isn't entirely desirable; however= , it + is better to have a small interface for now, and be able to change it eas= ily + later. The ideal situation (see 5.) is to run -rt tasks from a -deadline + server; in which case the -rt bandwidth is a direct subset of dl_bw. =20 This means that, for a root_domain comprising M CPUs, -deadline tasks can be created while the sum of their bandwidths stays below: diff --git a/Documentation/scheduler/sched-rt-group.rst b/Documentation/sch= eduler/sched-rt-group.rst index d685609ed3d7a..80b05a3009ea2 100644 --- a/Documentation/scheduler/sched-rt-group.rst +++ b/Documentation/scheduler/sched-rt-group.rst @@ -92,10 +92,10 @@ The system wide settings are configured under the /proc= virtual file system: /proc/sys/kernel/sched_rt_runtime_us: A global limit on how much time real-time scheduling may use. This is al= ways less or equal to the period_us, as it denotes the time allocated from the - period_us for the real-time tasks. Even without CONFIG_RT_GROUP_SCHED en= abled, - this will limit time reserved to real-time processes. With - CONFIG_RT_GROUP_SCHED=3Dy it signifies the total bandwidth available to = all - real-time groups. + period_us for the real-time tasks. Without CONFIG_RT_GROUP_SCHED enabled, + this only serves for admission control of deadline tasks. With + CONFIG_RT_GROUP_SCHED=3Dy it also signifies the total bandwidth availabl= e to + all real-time groups. =20 * Time is specified in us because the interface is s32. This gives an operating range from 1us to about 35 minutes. --=20 2.47.0