Re: [PATCH v2 00/17] sched/paravirt: Introduce cpu_preferred_mask and steal-driven vCPU backoff

[Shrikanth Hegde <sshegde@linux.ibm.com>]

> I will attach the irqbalance patch which detects the changes in this
> mask and re-adjusts the irq affinities. Series doesn't address when
> irqbalance=n. Assuming many distros have irqbalance=y by default.
> 

Subject: [PATCH] irqbalance: Check for changes in cpu_preferred_mask

---
  cputree.c    | 28 +++++++++++++++++++++++++++-
  irqbalance.c |  2 ++
  irqbalance.h |  1 +
  3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/cputree.c b/cputree.c
index 9baa264..1db3422 100644
--- a/cputree.c
+++ b/cputree.c
@@ -56,6 +56,11 @@ cpumask_t banned_cpus;
  
  cpumask_t cpu_online_map;
  
+/* This can dynamically change. If any change in mask detect
+ * and trigger a rebuild
+ */
+cpumask_t cpu_preferred_mask;
+
  /*
     it's convenient to have the complement of banned_cpus available so that
     the AND operator can be used to mask out unwanted cpus
@@ -506,15 +511,36 @@ void clear_work_stats(void)
  	for_each_object(numa_nodes, clear_obj_stats, NULL);
  }
  
+void parse_preferred_cpus(void)
+{
+	cpumask_t preferred;
+	char *path = NULL;
+
+	path = "/sys/devices/system/cpu/preferred";
+	cpus_clear(preferred);
+	process_one_line(path, get_mask_from_cpulist, &preferred);
+
+	/* Did anything change compared to earlier */
+	if (!cpus_equal(preferred, cpu_preferred_mask)) {
+		log(TO_CONSOLE, LOG_INFO, "cpu preferred mask changed\n");
+		need_rebuild = 1;
+	}
+
+	cpus_copy(cpu_preferred_mask, preferred);
+}
  
  void parse_cpu_tree(void)
  {
  	DIR *dir;
  	struct dirent *entry;
+	char buffer[4096];
  
  	setup_banned_cpus();
  
-	cpus_complement(unbanned_cpus, banned_cpus);
+	cpus_andnot(unbanned_cpus, cpu_preferred_mask, banned_cpus);
+
+	cpumask_scnprintf(buffer, 4096, unbanned_cpus);
+	log(TO_CONSOLE, LOG_INFO, "Unbanned CPUs: %s\n", buffer);
  
  	dir = opendir("/sys/devices/system/cpu");
  	if (!dir)
diff --git a/irqbalance.c b/irqbalance.c
index f80244c..f3d46b8 100644
--- a/irqbalance.c
+++ b/irqbalance.c
@@ -229,6 +229,7 @@ static void parse_command_line(int argc, char **argv)
  static void build_object_tree(void)
  {
  	build_numa_node_list();
+	parse_preferred_cpus();
  	parse_cpu_tree();
  	rebuild_irq_db();
  }
@@ -275,6 +276,7 @@ gboolean scan(gpointer data __attribute__((unused)))
  	log(TO_CONSOLE, LOG_INFO, "\n\n\n-----------------------------------------------------------------------------\n");
  	clear_work_stats();
  	parse_proc_interrupts();
+	parse_preferred_cpus();
  
  
  	/* cope with cpu hotplug -- detected during /proc/interrupts parsing */
diff --git a/irqbalance.h b/irqbalance.h
index 47e40cc..593b183 100644
--- a/irqbalance.h
+++ b/irqbalance.h
@@ -57,6 +57,7 @@ void migrate_irq_obj(struct topo_obj *from, struct topo_obj *to, struct irq_info
  void activate_mappings(void);
  void clear_cpu_tree(void);
  void free_cpu_topo(gpointer data);
+extern void parse_preferred_cpus(void);
  /*===================NEW BALANCER FUNCTIONS============================*/
  
  /*
-- 
2.47.3