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@xxxxxxxxxx>
AuthorDate: Wed, 30 Oct 2024 13:52:51 -04:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241030175253.125248-3-longman@xxxxxxxxxx
---
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;
}
|