linux-kernel - [PATCH 3/3] sched/isolation: Consolidate housekeeping cpumasks that are always identical

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Message-ID: <20240818234520.90186-4-longman@redhat.com>
Date: Sun, 18 Aug 2024 19:45:20 -0400
From: Waiman Long <longman@...hat.com>
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Frederic Weisbecker <frederic@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	Waiman Long <longman@...hat.com>
Subject: [PATCH 3/3] sched/isolation: Consolidate housekeeping cpumasks that are always identical

The housekeeping cpumasks are only set by two boot commandline
parameters: "nohz_full" and "isolcpus". When there is more than one of
"nohz_full" or "isolcpus", the extra ones must have the same CPU list
or the setup will fail partially.

The HK_TYPE_TICK, HK_TYPE_DOMAIN and HK_TYPE_MANAGED_IRQ types are
settable by "isolcpus" and they can be set individually. The other
housekeeping types are all set by "nohz_full" without a way to set them
individually. So they all have identical cpumasks.

There is actually no point to have different cpumasks for these
"nohz_full" only housekeeping types. Consolidate these types to use the
same cpumask by aliasing them to the same value. If there is a need to
set any of them independently in the future, we can break them out to
their own cpumasks again.

With this change, the number of cpumasks in the housekeeping structure
drops from 9 to 4.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/sched/isolation.h | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index 2b461129d1fa..da32b502f0c6 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -7,15 +7,22 @@
 #include <linux/tick.h>

 enum hk_type {
-	HK_TYPE_TIMER,
-	HK_TYPE_RCU,
-	HK_TYPE_MISC,
-	HK_TYPE_SCHED,
 	HK_TYPE_TICK,
 	HK_TYPE_DOMAIN,
-	HK_TYPE_WQ,
 	HK_TYPE_MANAGED_IRQ,
-	HK_TYPE_KTHREAD,
+	HK_TYPE_NOHZ_FULL,
+
+	/*
+	 * The following housekeeping types are only set by the nohz_full
+	 * boot commandline option. So they can share the same value.
+	 */
+	HK_TYPE_TIMER   = HK_TYPE_NOHZ_FULL,
+	HK_TYPE_RCU     = HK_TYPE_NOHZ_FULL,
+	HK_TYPE_MISC    = HK_TYPE_NOHZ_FULL,
+	HK_TYPE_SCHED   = HK_TYPE_NOHZ_FULL,
+	HK_TYPE_WQ      = HK_TYPE_NOHZ_FULL,
+	HK_TYPE_KTHREAD = HK_TYPE_NOHZ_FULL,
+
 	HK_TYPE_MAX
 };

-- 
2.43.5