Re: [RFC PATCH] rcu: move SRCU grace period work to power efficient workqueue
From: Mike Galbraith
Date: Wed Feb 19 2014 - 02:00:48 EST
On Mon, 2014-02-17 at 05:50 +0100, Mike Galbraith wrote:
> On Sun, 2014-02-16 at 08:41 -0800, Paul E. McKenney wrote:
> > So maybe start with Kevin's patch, but augment with something else for
> > the !NO_HZ_FULL case?
>
> Sure (hm, does it work without workqueue.disable_numa ?).
I took patch out for a spin on a 40 core box +SMT, with CPUs 4-79
isolated via exclusive cpuset with load balancing off. Worker bees
ignored patch either way.
-Mike
Perturbation measurement hog pinned to CPU4.
With patch:
# TASK-PID CPU# |||||| TIMESTAMP FUNCTION
# | | | |||||| | |
pert-9949 [004] ....113 405.120164: workqueue_queue_work: work struct=ffff880a5c4ecc08 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=4
pert-9949 [004] ....113 405.120166: workqueue_activate_work: work struct ffff880a5c4ecc08
pert-9949 [004] d.L.313 405.120169: sched_wakeup: comm=kworker/4:2 pid=2119 prio=120 success=1 target_cpu=004
pert-9949 [004] d.Lh213 405.120170: tick_stop: success=no msg=more than 1 task in runqueue
pert-9949 [004] d.L.213 405.120172: tick_stop: success=no msg=more than 1 task in runqueue
pert-9949 [004] d...3.. 405.120173: sched_switch: prev_comm=pert prev_pid=9949 prev_prio=120 prev_state=R+ ==> next_comm=kworker/4:2 next_pid=2119 next_prio=120
kworker/4:2-2119 [004] ....1.. 405.120174: workqueue_execute_start: work struct ffff880a5c4ecc08: function flush_to_ldisc
kworker/4:2-2119 [004] d...311 405.120176: sched_wakeup: comm=sshd pid=6620 prio=120 success=1 target_cpu=000
kworker/4:2-2119 [004] ....1.. 405.120176: workqueue_execute_end: work struct ffff880a5c4ecc08
kworker/4:2-2119 [004] d...3.. 405.120177: sched_switch: prev_comm=kworker/4:2 prev_pid=2119 prev_prio=120 prev_state=S ==> next_comm=pert next_pid=9949 next_prio=120
pert-9949 [004] ....113 405.120178: workqueue_queue_work: work struct=ffff880a5c4ecc08 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=4
pert-9949 [004] ....113 405.120179: workqueue_activate_work: work struct ffff880a5c4ecc08
pert-9949 [004] d.L.313 405.120179: sched_wakeup: comm=kworker/4:2 pid=2119 prio=120 success=1 target_cpu=004
pert-9949 [004] d.L.213 405.120181: tick_stop: success=no msg=more than 1 task in runqueue
pert-9949 [004] d...3.. 405.120181: sched_switch: prev_comm=pert prev_pid=9949 prev_prio=120 prev_state=R+ ==> next_comm=kworker/4:2 next_pid=2119 next_prio=120
kworker/4:2-2119 [004] ....1.. 405.120182: workqueue_execute_start: work struct ffff880a5c4ecc08: function flush_to_ldisc
kworker/4:2-2119 [004] ....1.. 405.120183: workqueue_execute_end: work struct ffff880a5c4ecc08
kworker/4:2-2119 [004] d...3.. 405.120183: sched_switch: prev_comm=kworker/4:2 prev_pid=2119 prev_prio=120 prev_state=S ==> next_comm=pert next_pid=9949 next_prio=120
pert-9949 [004] d...1.. 405.120736: tick_stop: success=yes msg=
pert-9949 [004] ....113 410.121082: workqueue_queue_work: work struct=ffff880a5c4ecc08 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=4
pert-9949 [004] ....113 410.121082: workqueue_activate_work: work struct ffff880a5c4ecc08
pert-9949 [004] d.L.313 410.121084: sched_wakeup: comm=kworker/4:2 pid=2119 prio=120 success=1 target_cpu=004
pert-9949 [004] d.Lh213 410.121085: tick_stop: success=no msg=more than 1 task in runqueue
pert-9949 [004] d.L.213 410.121087: tick_stop: success=no msg=more than 1 task in runqueue
...and so on until tick time
(extra cheezy) hack kinda sorta works iff workqueue.disable_numa:
---
kernel/workqueue.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1328,8 +1328,11 @@ static void __queue_work(int cpu, struct
rcu_read_lock();
retry:
- if (req_cpu == WORK_CPU_UNBOUND)
+ if (req_cpu == WORK_CPU_UNBOUND) {
cpu = raw_smp_processor_id();
+ if (runqueue_is_isolated(cpu))
+ cpu = 0;
+ }
/* pwq which will be used unless @work is executing elsewhere */
if (!(wq->flags & WQ_UNBOUND))
# TASK-PID CPU# |||||| TIMESTAMP FUNCTION
# | | | |||||| | |
<...>-33824 [004] ....113 5555.889694: workqueue_queue_work: work struct=ffff880a596eb008 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=0
<...>-33824 [004] ....113 5555.889695: workqueue_activate_work: work struct ffff880a596eb008
<...>-33824 [004] d...313 5555.889697: sched_wakeup: comm=kworker/0:2 pid=2105 prio=120 success=1 target_cpu=000
<...>-33824 [004] ....113 5560.890594: workqueue_queue_work: work struct=ffff880a596eb008 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=0
<...>-33824 [004] ....113 5560.890595: workqueue_activate_work: work struct ffff880a596eb008
<...>-33824 [004] d...313 5560.890596: sched_wakeup: comm=kworker/0:2 pid=2105 prio=120 success=1 target_cpu=000
<...>-33824 [004] ....113 5565.891493: workqueue_queue_work: work struct=ffff880a596eb008 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=0
<...>-33824 [004] ....113 5565.891493: workqueue_activate_work: work struct ffff880a596eb008
<...>-33824 [004] d...313 5565.891494: sched_wakeup: comm=kworker/0:2 pid=2105 prio=120 success=1 target_cpu=000
<...>-33824 [004] ....113 5570.892401: workqueue_queue_work: work struct=ffff880a596eb008 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=0
<...>-33824 [004] ....113 5570.892401: workqueue_activate_work: work struct ffff880a596eb008
<...>-33824 [004] d...313 5570.892403: sched_wakeup: comm=kworker/0:2 pid=2105 prio=120 success=1 target_cpu=000
<...>-33824 [004] ....113 5575.893300: workqueue_queue_work: work struct=ffff880a596eb008 function=flush_to_ldisc workqueue=ffff88046f40ba00 req_cpu=256 cpu=0
<...>-33824 [004] ....113 5575.893301: workqueue_activate_work: work struct ffff880a596eb008
<...>-33824 [004] d...313 5575.893302: sched_wakeup: comm=kworker/0:2 pid=2105 prio=120 success=1 target_cpu=000
<...>-33824 [004] d..h1.. 5578.854979: softirq_raise: vec=1 [action=TIMER]
<...>-33824 [004] dN..3.. 5578.854981: sched_wakeup: comm=sirq-timer/4 pid=319 prio=69 success=1 target_cpu=004
<...>-33824 [004] dN..1.. 5578.854982: tick_stop: success=no msg=more than 1 task in runqueue
<...>-33824 [004] dN.h1.. 5578.854983: tick_stop: success=no msg=more than 1 task in runqueue
<...>-33824 [004] dN..1.. 5578.854985: tick_stop: success=no msg=more than 1 task in runqueue
<...>-33824 [004] d...3.. 5578.854986: sched_switch: prev_comm=pert prev_pid=33824 prev_prio=120 prev_state=R+ ==> next_comm=sirq-timer/4 next_pid=319 next_prio=69
sirq-timer/4-319 [004] d..h3.. 5578.854987: softirq_raise: vec=1 [action=TIMER]
sirq-timer/4-319 [004] d...3.. 5578.854989: tick_stop: success=no msg=more than 1 task in runqueue
sirq-timer/4-319 [004] ....111 5578.854990: softirq_entry: vec=1 [action=TIMER]
sirq-timer/4-319 [004] ....111 5578.855194: softirq_exit: vec=1 [action=TIMER] <== 204us tick, not good... to_stare_at++
sirq-timer/4-319 [004] d...3.. 5578.855196: sched_switch: prev_comm=sirq-timer/4 prev_pid=319 prev_prio=69 prev_state=S ==> next_comm=pert next_pid=33824 next_prio=120
<...>-33824 [004] d...1.. 5578.855987: tick_stop: success=yes msg=
...etc
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