From: Ankur Arora <ankur.a.arora@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, peterz@infradead.org,
torvalds@linux-foundation.org, paulmck@kernel.org,
akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
willy@infradead.org, mgorman@suse.de, jpoimboe@kernel.org,
mark.rutland@arm.com, jgross@suse.com, andrew.cooper3@citrix.com,
bristot@kernel.org, mathieu.desnoyers@efficios.com,
geert@linux-m68k.org, glaubitz@physik.fu-berlin.de,
anton.ivanov@cambridgegreys.com, mattst88@gmail.com,
krypton@ulrich-teichert.org, rostedt@goodmis.org,
David.Laight@ACULAB.COM, richard@nod.at, mjguzik@gmail.com,
jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com,
boris.ostrovsky@oracle.com, konrad.wilk@oracle.com,
Ankur Arora <ankur.a.arora@oracle.com>
Subject: [PATCH 25/30] sched: support preempt=full under PREEMPT_AUTO
Date: Mon, 12 Feb 2024 21:55:49 -0800 [thread overview]
Message-ID: <20240213055554.1802415-26-ankur.a.arora@oracle.com> (raw)
In-Reply-To: <20240213055554.1802415-1-ankur.a.arora@oracle.com>
The default preemption policy for preempt-full under PREEMPT_AUTO is
to minimize latency, and thus to always schedule eagerly. This is
identical to CONFIG_PREEMPT, and so should result in similar
performance.
Comparing scheduling/IPC workload:
# perf stat -a -e cs --repeat 10 -- perf bench sched messaging -g 20 -t -l 5000
PREEMPT_AUTO, preempt=full
3,080,508 context-switches ( +- 0.64% )
3.65171 +- 0.00654 seconds time elapsed ( +- 0.18% )
PREEMPT_DYNAMIC, preempt=full
3,087,527 context-switches ( +- 0.33% )
3.60163 +- 0.00633 seconds time elapsed ( +- 0.18% )
Looking at the breakup between voluntary and involuntary context-switches, we
see almost identical behaviour as well.
PREEMPT_AUTO, preempt=full
2087910.00 +- 34720.95 voluntary context-switches ( +- 1.660% )
784437.60 +- 19827.79 involuntary context-switches ( +- 2.520% )
PREEMPT_DYNAMIC, preempt=full
2102879.60 +- 22767.11 voluntary context-switches ( +- 1.080% )
801189.90 +- 21324.18 involuntary context-switches ( +- 2.660% )
Comparing kernbench half load (-j 32), we see that both voluntary
and involuntary context switches, and their stdev is fairly similar.
So is the percentage of CPU taken and various process times.
# Half load (-j 32)
PREEMPT_AUTO PREEMPT_DYNAMIC
wall 74.45 +- 0.39 sec ( +- 0.53% ) 74.08 +- 0.20 sec ( +- 0.27% )
utime 1419.68 +- 5.12 sec ( +- 0.36% ) 1419.76 +- 3.63 sec ( +- 0.25% )
stime 250.56 +- 1.08 sec ( +- 0.43% ) 248.94 +- 0.80 sec ( +- 0.32% )
%cpu 2243.20 +- 19.57 ( +- 0.87% ) 2251.80 +- 11.12 ( +- 0.49% )
inv-csw 20286.60 +- 547.48 ( +- 2.69% ) 20175.60 +- 214.20 ( +- 1.06% )
vol-csw 187688.00 +- 5097.26 ( +- 2.71% ) 182914.00 +- 2525.59 ( +- 1.38% )
Same for kernbench optimal and maximal loads.
# Optimal load (-j 256)
PREEMPT_AUTO PREEMPT_DYNAMIC
wall 65.10 +- 0.09 sec ( +- 0.14% ) 65.11 +- 0.27 sec ( +- 0.42% )
utime 1875.03 +- 479.98 sec ( +- 25.59% ) 1874.55 +- 479.39 sec ( +- 25.57% )
stime 297.70 +- 49.68 sec ( +- 16.69% ) 297.04 +- 50.69 sec ( +- 17.06% )
%cpu 3175.60 +- 982.93 ( +- 30.95% ) 3179.40 +- 977.87 ( +- 30.75% )
inv-csw 391147.00 +- 390941.00 ( +- 99.94% ) 392298.00 +- 392268.00 ( +- 99.99% )
vol-csw 212039.00 +- 26419.90 ( +- 12.45% ) 211349.00 +- 30227.30 ( +- 14.30% )
# Maximal load (-j 256)
PREEMPT_AUTO PREEMPT_DYNAMIC
wall 66.55 +- 0.34 sec ( +- 0.51% ) 66.41 +- 0.72 sec ( +- 1.09% )
utime 2028.83 +- 445.86 sec ( +- 21.97% ) 2027.59 +- 444.89 sec ( +- 21.94% )
stime 316.16 +- 48.29 sec ( +- 15.27% ) 313.97 +- 47.61 sec ( +- 15.16% )
%cpu 3463.93 +- 894.12 ( +- 25.81% ) 3465.33 +- 889.04 ( +- 25.65% )
inv-csw 491115.00 +- 345936.00 ( +- 70.43% ) 492028.00 +- 346745.00 ( +- 70.47% )
vol-csw 200509.00 +- 32922.60 ( +- 16.41% ) 187447.00 +- 42567.20 ( +- 22.70% )
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Ziljstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
---
kernel/sched/core.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2d33f3ff51a3..aaa87d5fecdd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1035,8 +1035,9 @@ void wake_up_q(struct wake_q_head *head)
* For preemption models other than PREEMPT_AUTO: always schedule
* eagerly.
*
- * For PREEMPT_AUTO: schedule idle threads eagerly, allow everything
- * else, whether running in user or kernel context, to finish its time
+ * For PREEMPT_AUTO: schedule idle threads eagerly, and under full
+ * preemption all tasks eagerly. Otherwise, allow everything else,
+ * whether running in user or kernel context, to finish its time
* quanta, and mark for rescheduling at the next exit to user.
*
* Note: to avoid the hog problem, where the user does not relinquish
@@ -1052,6 +1053,9 @@ static resched_t resched_opt_translate(struct task_struct *curr,
if (opt == RESCHED_FORCE)
return NR_now;
+ if (preempt_model_preemptible())
+ return NR_now;
+
if (is_idle_task(curr))
return NR_now;
@@ -8982,7 +8986,9 @@ static void __sched_dynamic_update(int mode)
pr_warn("%s: preempt=full is not recommended with CONFIG_PREEMPT_RCU=n",
PREEMPT_MODE);
- preempt_dynamic_mode = preempt_dynamic_undefined;
+ if (mode != preempt_dynamic_mode)
+ pr_info("%s: full\n", PREEMPT_MODE);
+ preempt_dynamic_mode = mode;
break;
}
}
--
2.31.1
next prev parent reply other threads:[~2024-02-13 5:57 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-13 5:55 [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling Ankur Arora
2024-02-13 5:55 ` [PATCH 01/30] preempt: introduce CONFIG_PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 02/30] thread_info: selector for TIF_NEED_RESCHED[_LAZY] Ankur Arora
2024-02-19 15:16 ` Thomas Gleixner
2024-02-20 22:50 ` Ankur Arora
2024-02-21 17:05 ` Thomas Gleixner
2024-02-21 18:26 ` Steven Rostedt
2024-02-21 20:03 ` Thomas Gleixner
2024-02-13 5:55 ` [PATCH 03/30] thread_info: tif_need_resched() now takes resched_t as param Ankur Arora
2024-02-14 3:17 ` kernel test robot
2024-02-14 14:08 ` Mark Rutland
2024-02-15 4:08 ` Ankur Arora
2024-02-19 12:30 ` Mark Rutland
2024-02-20 22:09 ` Ankur Arora
2024-02-19 15:21 ` Thomas Gleixner
2024-02-20 22:21 ` Ankur Arora
2024-02-21 17:07 ` Thomas Gleixner
2024-02-21 21:22 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 04/30] sched: make test_*_tsk_thread_flag() return bool Ankur Arora
2024-02-14 14:12 ` Mark Rutland
2024-02-15 2:04 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 05/30] sched: *_tsk_need_resched() now takes resched_t as param Ankur Arora
2024-02-19 15:26 ` Thomas Gleixner
2024-02-20 22:37 ` Ankur Arora
2024-02-21 17:10 ` Thomas Gleixner
2024-02-13 5:55 ` [PATCH 06/30] entry: handle lazy rescheduling at user-exit Ankur Arora
2024-02-19 15:29 ` Thomas Gleixner
2024-02-20 22:38 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 07/30] entry/kvm: handle lazy rescheduling at guest-entry Ankur Arora
2024-02-13 5:55 ` [PATCH 08/30] entry: irqentry_exit only preempts for TIF_NEED_RESCHED Ankur Arora
2024-02-13 5:55 ` [PATCH 09/30] sched: __schedule_loop() doesn't need to check for need_resched_lazy() Ankur Arora
2024-02-13 5:55 ` [PATCH 10/30] sched: separate PREEMPT_DYNAMIC config logic Ankur Arora
2024-02-13 5:55 ` [PATCH 11/30] sched: runtime preemption config under PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 12/30] rcu: limit PREEMPT_RCU to full preemption " Ankur Arora
2024-02-13 5:55 ` [PATCH 13/30] rcu: fix header guard for rcu_all_qs() Ankur Arora
2024-02-13 5:55 ` [PATCH 14/30] preempt,rcu: warn on PREEMPT_RCU=n, preempt=full Ankur Arora
2024-02-13 5:55 ` [PATCH 15/30] rcu: handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y Ankur Arora
2024-03-10 10:03 ` Joel Fernandes
2024-03-10 18:56 ` Paul E. McKenney
2024-03-11 0:48 ` Joel Fernandes
2024-03-11 3:56 ` Paul E. McKenney
2024-03-11 15:01 ` Joel Fernandes
2024-03-11 20:51 ` Ankur Arora
2024-03-11 22:12 ` Thomas Gleixner
2024-03-11 5:18 ` Ankur Arora
2024-03-11 15:25 ` Joel Fernandes
2024-03-11 19:12 ` Thomas Gleixner
2024-03-11 19:53 ` Paul E. McKenney
2024-03-11 20:29 ` Thomas Gleixner
2024-03-12 0:01 ` Paul E. McKenney
2024-03-12 0:08 ` Joel Fernandes
2024-03-12 3:16 ` Ankur Arora
2024-03-12 3:24 ` Joel Fernandes
2024-03-12 5:23 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 16/30] rcu: force context-switch " Ankur Arora
2024-02-13 5:55 ` [PATCH 17/30] x86/thread_info: define TIF_NEED_RESCHED_LAZY Ankur Arora
2024-02-14 13:25 ` Mark Rutland
2024-02-14 20:31 ` Ankur Arora
2024-02-19 12:32 ` Mark Rutland
2024-02-13 5:55 ` [PATCH 18/30] sched: prepare for lazy rescheduling in resched_curr() Ankur Arora
2024-02-13 5:55 ` [PATCH 19/30] sched: default preemption policy for PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 20/30] sched: handle idle preemption " Ankur Arora
2024-02-13 5:55 ` [PATCH 21/30] sched: schedule eagerly in resched_cpu() Ankur Arora
2024-02-13 5:55 ` [PATCH 22/30] sched/fair: refactor update_curr(), entity_tick() Ankur Arora
2024-02-13 5:55 ` [PATCH 23/30] sched/fair: handle tick expiry under lazy preemption Ankur Arora
2024-02-21 21:38 ` Steven Rostedt
2024-02-28 13:47 ` Juri Lelli
2024-02-29 6:43 ` Ankur Arora
2024-02-29 9:33 ` Juri Lelli
2024-02-29 23:54 ` Ankur Arora
2024-03-01 0:28 ` Paul E. McKenney
2024-02-13 5:55 ` [PATCH 24/30] sched: support preempt=none under PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` Ankur Arora [this message]
2024-02-13 5:55 ` [PATCH 26/30] sched: handle preempt=voluntary " Ankur Arora
2024-03-03 1:08 ` Joel Fernandes
2024-03-05 8:11 ` Ankur Arora
2024-03-06 20:42 ` Joel Fernandes
2024-03-07 19:01 ` Paul E. McKenney
2024-03-08 0:15 ` Joel Fernandes
2024-03-08 0:42 ` Paul E. McKenney
2024-03-08 4:22 ` Ankur Arora
2024-03-08 21:33 ` Paul E. McKenney
2024-03-11 4:50 ` Ankur Arora
2024-03-11 19:26 ` Paul E. McKenney
2024-03-11 20:09 ` Ankur Arora
2024-03-11 20:23 ` Linus Torvalds
2024-03-11 21:03 ` Ankur Arora
2024-03-12 0:03 ` Paul E. McKenney
2024-03-12 12:14 ` Thomas Gleixner
2024-03-12 19:40 ` Paul E. McKenney
2024-03-08 3:49 ` Ankur Arora
2024-03-08 5:29 ` Joel Fernandes
2024-03-08 6:54 ` Juri Lelli
2024-03-11 5:34 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 27/30] sched: latency warn for TIF_NEED_RESCHED_LAZY Ankur Arora
2024-02-13 5:55 ` [PATCH 28/30] tracing: support lazy resched Ankur Arora
2024-02-13 5:55 ` [PATCH 29/30] Documentation: tracing: add TIF_NEED_RESCHED_LAZY Ankur Arora
2024-02-21 21:43 ` Steven Rostedt
2024-02-21 23:22 ` Ankur Arora
2024-02-21 23:53 ` Steven Rostedt
2024-03-01 23:33 ` Joel Fernandes
2024-03-02 3:09 ` Ankur Arora
2024-03-03 19:32 ` Joel Fernandes
2024-02-13 5:55 ` [PATCH 30/30] osnoise: handle quiescent states for PREEMPT_RCU=n, PREEMPTION=y Ankur Arora
2024-02-13 9:47 ` [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling Geert Uytterhoeven
2024-02-13 21:46 ` Ankur Arora
2024-02-14 23:57 ` Paul E. McKenney
2024-02-15 2:03 ` Ankur Arora
2024-02-15 3:45 ` Paul E. McKenney
2024-02-15 19:28 ` Paul E. McKenney
2024-02-15 20:04 ` Thomas Gleixner
2024-02-15 20:54 ` Paul E. McKenney
2024-02-15 20:53 ` Ankur Arora
2024-02-15 20:55 ` Paul E. McKenney
2024-02-15 21:24 ` Ankur Arora
2024-02-15 22:54 ` Paul E. McKenney
2024-02-15 22:56 ` Paul E. McKenney
2024-02-16 0:45 ` Ankur Arora
2024-02-16 2:59 ` Paul E. McKenney
2024-02-17 0:55 ` Paul E. McKenney
2024-02-17 3:59 ` Ankur Arora
2024-02-18 18:17 ` Paul E. McKenney
2024-02-19 16:48 ` Paul E. McKenney
2024-02-21 18:19 ` Steven Rostedt
2024-02-21 19:41 ` Paul E. McKenney
2024-02-21 20:11 ` Steven Rostedt
2024-02-21 20:22 ` Paul E. McKenney
2024-02-22 15:50 ` Mark Rutland
2024-02-22 19:11 ` Paul E. McKenney
2024-02-23 11:05 ` Mark Rutland
2024-02-23 15:31 ` Paul E. McKenney
2024-03-02 1:16 ` Paul E. McKenney
2024-03-19 11:45 ` Tasks RCU, ftrace, and trampolines (was: Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling) Mark Rutland
2024-03-19 23:33 ` Paul E. McKenney
2024-02-21 6:48 ` [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling Ankur Arora
2024-02-21 17:44 ` Paul E. McKenney
2024-02-16 0:45 ` Ankur Arora
2024-02-21 12:23 ` Raghavendra K T
2024-02-21 17:15 ` Thomas Gleixner
2024-02-21 17:27 ` Raghavendra K T
2024-02-21 21:16 ` Ankur Arora
2024-02-22 4:05 ` Raghavendra K T
2024-02-22 21:23 ` Thomas Gleixner
2024-02-23 3:14 ` Ankur Arora
2024-02-23 6:28 ` Raghavendra K T
2024-02-24 3:15 ` Raghavendra K T
2024-02-27 17:45 ` Ankur Arora
2024-02-22 13:04 ` Raghavendra K T
2024-04-23 15:21 ` Shrikanth Hegde
2024-04-23 16:13 ` Linus Torvalds
2024-04-26 7:46 ` Shrikanth Hegde
2024-04-26 19:00 ` Ankur Arora
2024-05-07 11:16 ` Shrikanth Hegde
2024-05-08 5:18 ` Ankur Arora
2024-05-15 14:31 ` Shrikanth Hegde
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