[PATCH 4/7] sched/isolation: Isolate workqueues when "nohz_full=" is set

[Frederic Weisbecker]

As we prepare for offloading the residual 1hz scheduler ticks to
workqueue, let's affine those to housekeepers so that they don't
interrupt the CPUs that don't want to be disturbed.

Reviewed-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Frederic Weisbecker <frede...@kernel.org>
Cc: Chris Metcalf <cmetc...@mellanox.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Luiz Capitulino <lcapitul...@redhat.com>
Cc: Mike Galbraith <efa...@gmx.de>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Rik van Riel <r...@redhat.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Wanpeng Li <kernel...@gmail.com>
Cc: Ingo Molnar <mi...@kernel.org>
---
 include/linux/sched/isolation.h | 1 +
 kernel/sched/isolation.c        | 3 ++-
 kernel/workqueue.c              | 3 ++-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
index d849431..4a6582c 100644
--- a/include/linux/sched/isolation.h
+++ b/include/linux/sched/isolation.h
@@ -12,6 +12,7 @@ enum hk_flags {
        HK_FLAG_SCHED           = (1 << 3),
        HK_FLAG_TICK            = (1 << 4),
        HK_FLAG_DOMAIN          = (1 << 5),
+       HK_FLAG_WQ              = (1 << 6),
 };
 
 #ifdef CONFIG_CPU_ISOLATION
diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index b71b436..a2500c4 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -3,6 +3,7 @@
  *  any CPU: unbound workqueues, timers, kthreads and any offloadable work.
  *
  * Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
+ * Copyright (C) 2017-2018 SUSE, Frederic Weisbecker
  *
  */
 
@@ -119,7 +120,7 @@ static int __init housekeeping_nohz_full_setup(char *str)
 {
        unsigned int flags;
 
-       flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+       flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU | 
HK_FLAG_MISC;
 
        return housekeeping_setup(str, flags);
 }
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 017044c..593dbe7 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5565,12 +5565,13 @@ static void __init wq_numa_init(void)
 int __init workqueue_init_early(void)
 {
        int std_nice[NR_STD_WORKER_POOLS] = { 0, HIGHPRI_NICE_LEVEL };
+       int hk_flags = HK_FLAG_DOMAIN | HK_FLAG_WQ;
        int i, cpu;
 
        WARN_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
 
        BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
-       cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_FLAG_DOMAIN));
+       cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(hk_flags));
 
        pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
 
-- 
2.7.4