Commit 1174b934 authored by Waiman Long's avatar Waiman Long Committed by Peter Zijlstra
Browse files

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: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20241030175253.125248-3-longman@redhat.com
parent ae5c6777

Documentation/admin-guide/kernel-parameters.txt

+3 −1
Original line number Diff line number Diff line
@@ -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

kernel/sched/isolation.c

+5 −1
Original line number Diff line number Diff line
@@ -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;

		}