From cfb15f0bb95ebfd4357708eae42febe9f2121fba Mon Sep 17 00:00:00 2001

From: Tao Liu <ltao@redhat.com>

Date: Wed, 13 Jul 2022 17:11:40 +0800

Subject: [PATCH 14/14] Improve documentation and logging for banned cpus

This patch have no functional modification. Just improve the doc and log

for isolcpu, nohz_full and numa node banning cpus, for providing more

info for users.

Signed-off-by: Tao Liu <ltao@redhat.com>

---

 cputree.c    | 6 +++---

 irqbalance.1 | 2 +-

 placement.c  | 6 +++++-

 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/cputree.c b/cputree.c

index c250977..eb1981e 100644

--- a/cputree.c

+++ b/cputree.c

@@ -159,14 +159,14 @@ static void setup_banned_cpus(void)

 	cpus_or(banned_cpus, nohz_full, isolated_cpus);

 	cpumask_scnprintf(buffer, 4096, isolated_cpus);

-	log(TO_CONSOLE, LOG_INFO, "Isolated CPUs: %s\n", buffer);

+	log(TO_CONSOLE, LOG_INFO, "Prevent irq assignment to these isolated CPUs: %s\n", buffer);

 	cpumask_scnprintf(buffer, 4096, nohz_full);

-	log(TO_CONSOLE, LOG_INFO, "Adaptive-ticks CPUs: %s\n", buffer);

+	log(TO_CONSOLE, LOG_INFO, "Prevent irq assignment to these adaptive-ticks CPUs: %s\n", buffer);

 out:

 #ifdef HAVE_THERMAL

 	cpus_or(banned_cpus, banned_cpus, thermal_banned_cpus);

 	cpumask_scnprintf(buffer, 4096, thermal_banned_cpus);

-	log(TO_CONSOLE, LOG_INFO, "Thermal-banned CPUs: %s\n", buffer);

+	log(TO_CONSOLE, LOG_INFO, "Prevent irq assignment to these thermal-banned CPUs: %s\n", buffer);

 #endif

 	cpumask_scnprintf(buffer, 4096, banned_cpus);

 	log(TO_CONSOLE, LOG_INFO, "Banned CPUs: %s\n", buffer);

diff --git a/irqbalance.1 b/irqbalance.1

index 361faea..4c75362 100644

--- a/irqbalance.1

+++ b/irqbalance.1

@@ -167,7 +167,7 @@ Same as --debug.

 .B IRQBALANCE_BANNED_CPUS

 Provides a mask of CPUs which irqbalance should ignore and never assign interrupts to.

 If not specified, irqbalance use mask of isolated and adaptive-ticks CPUs on the

-system as the default value.

+system as the default value. The "isolcpus=" boot parameter specifies the isolated CPUs. The "nohz_full=" boot parameter specifies the adaptive-ticks CPUs. By default, no CPU will be an isolated or adaptive-ticks CPU.

 This is a hexmask without the leading ’0x’. On systems with large numbers of

 processors, each group of eight hex digits is separated by a comma ’,’. i.e.

 ‘export IRQBALANCE_BANNED_CPUS=fc0‘ would prevent irqbalance from assigning irqs

diff --git a/placement.c b/placement.c

index 17a9f2e..9fde8cb 100644

--- a/placement.c

+++ b/placement.c

@@ -135,8 +135,12 @@ static void place_irq_in_node(struct irq_info *info, void *data __attribute__((u

 		 * Need to make sure this node is elligible for migration

 		 * given the banned cpu list

 		 */

-		if (!cpus_intersects(irq_numa_node(info)->mask, unbanned_cpus))

+		if (!cpus_intersects(irq_numa_node(info)->mask, unbanned_cpus)) {

+			log(TO_CONSOLE, LOG_WARNING, "There is no suitable CPU in node:%d.\n", irq_numa_node(info)->number);

+			log(TO_CONSOLE, LOG_WARNING, "Irqbalance dispatch irq:%d to other node.\n", info->irq);

 			goto find_placement;

+		}

+

 		/*

 		 * This irq belongs to a device with a preferred numa node

 		 * put it on that node

-- 

2.33.1