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sched/isolation: Make "isolcpus=nohz" equivalent to "nohz_full"

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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
This commit is contained in:
Waiman Long 2024-10-30 13:52:51 -04:00 committed by Peter Zijlstra
parent ae5c677729
commit 1174b9344b
2 changed files with 8 additions and 2 deletions
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4
Documentation/admin-guide/kernel-parameters.txt
View File

@ -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

6
kernel/sched/isolation.c
View File

@ -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;
}