[PATCH] workqueue: for NO_HZ_FULL, set default cpumask to !tick_nohz_full_mask

[Kevin Hilman]

To help in keeping NO_HZ_FULL CPUs isolated, keep unbound workqueues
from running on full dynticks CPUs.  To do this, set the default
workqueue cpumask to be the set of "housekeeping" CPUs instead of all
possible CPUs.

This is just just the starting/default cpumask, and can be overridden
with all the normal ways (NUMA settings, apply_workqueue_attrs and via
sysfs for workqueus with the WQ_SYSFS attribute.)

Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Paul McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Kevin Hilman <khilman@xxxxxxxxxx>
---
 kernel/workqueue.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 987293d03ebc..9a9d9b0eaf6d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -48,6 +48,7 @@
 #include <linux/nodemask.h>
 #include <linux/moduleparam.h>
 #include <linux/uaccess.h>
+#include <linux/tick.h>
 
 #include "workqueue_internal.h"
 
@@ -3436,7 +3437,11 @@ struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask)
 	if (!alloc_cpumask_var(&attrs->cpumask, gfp_mask))
 		goto fail;
 
+#ifdef CONFIG_NO_HZ_FULL
+	cpumask_complement(attrs->cpumask, tick_nohz_full_mask);
+#else
 	cpumask_copy(attrs->cpumask, cpu_possible_mask);
+#endif
 	return attrs;
 fail:
 	free_workqueue_attrs(attrs);
-- 
1.8.3

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