Messages in this thread Patch in this message |  | | Date | Tue, 03 Dec 2024 10:44:38 -0000 | | From | "tip-bot2 for Waiman Long" <> | | Subject | [tip: sched/core] sched/isolation: Make "isolcpus=nohz" equivalent to "nohz_full" |
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The following commit has been merged into the sched/core branch of tip:
Commit-ID: 1174b9344bc7e7989439cad207fcd94eaab028db Gitweb: https://git.kernel.org/tip/1174b9344bc7e7989439cad207fcd94eaab028db Author: Waiman Long <longman@redhat.com> AuthorDate: Wed, 30 Oct 2024 13:52:51 -04:00 Committer: Peter Zijlstra <peterz@infradead.org> CommitterDate: Mon, 02 Dec 2024 12:24:28 +01:00
sched/isolation: Make "isolcpus=nohz" equivalent to "nohz_full"
The "isolcpus=nohz" boot parameter and flag were used to disable tick when running a single task. Nowsdays, this "nohz" flag is seldomly used as it is included as part of the "nohz_full" parameter. Extend this flag to cover other kernel noises disabled by the "nohz_full" parameter to make them equivalent. This also eliminates the need to use both the "isolcpus" and the "nohz_full" parameters to fully isolated a given set of CPUs.
Suggested-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20241030175253.125248-3-longman@redhat.com --- Documentation/admin-guide/kernel-parameters.txt | 4 +++- kernel/sched/isolation.c | 6 +++++- 2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3872bc6..3fa0b4e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2432,7 +2432,9 @@ specified in the flag list (default: domain): nohz - Disable the tick when a single task runs. + Disable the tick when a single task runs as well as + disabling other kernel noises like having RCU callbacks + offloaded. This is equivalent to the nohz_full parameter. A residual 1Hz tick is offloaded to workqueues, which you need to affine to housekeeping through the global diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 5345e11..6a68632 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -209,9 +209,13 @@ static int __init housekeeping_isolcpus_setup(char *str) int len; while (isalpha(*str)) { + /* + * isolcpus=nohz is equivalent to nohz_full. + */ if (!strncmp(str, "nohz,", 5)) { str += 5; - flags |= HK_FLAG_TICK; + flags |= HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | + HK_FLAG_RCU | HK_FLAG_MISC | HK_FLAG_KTHREAD; continue; }
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