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Subject[PATCH 3/6] sched/isolation: Isolate workqueues when "nohz_full=" is set
Date
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.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
---
include/linux/sched/isolation.h | 1 +
kernel/sched/isolation.c | 4 +++-
kernel/workqueue.c | 3 ++-
3 files changed, 6 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..8f1c1de 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 +120,8 @@ 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..0cee2d6 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5570,7 +5570,8 @@ int __init workqueue_init_early(void)
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_FLAG_DOMAIN | HK_FLAG_WQ));

pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);

--
2.7.4
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