From: Peter Zijlstra <peterz@infradead.org>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: bristot@redhat.com, bsegall@google.com, dietmar.eggemann@arm.com,
greg@kroah.com, gregkh@linuxfoundation.org, joshdon@google.com,
juri.lelli@redhat.com, linux-kernel@vger.kernel.org,
linux@rasmusvillemoes.dk, mgorman@suse.de, mingo@kernel.org,
rostedt@goodmis.org, valentin.schneider@arm.com,
vincent.guittot@linaro.org, linux-s390@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: sched: Move SCHED_DEBUG sysctl to debugfs
Date: Wed, 28 Apr 2021 11:25:19 +0200 [thread overview]
Message-ID: <YIkp/6/NDL7KsvpY@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <cf2a6c6c-21ea-df7b-94d1-940a344b8d26@de.ibm.com>
On Wed, Apr 28, 2021 at 10:54:37AM +0200, Christian Borntraeger wrote:
>
>
> On 28.04.21 10:46, Peter Zijlstra wrote:
> > On Tue, Apr 27, 2021 at 04:59:25PM +0200, Christian Borntraeger wrote:
> > > Peter,
> > >
> > > I just realized that we moved away sysctl tunabled to debugfs in next.
> > > We have seen several cases where it was benefitial to set
> > > sched_migration_cost_ns to a lower value. For example with KVM I can
> > > easily get 50% more transactions with 50000 instead of 500000.
> > > Until now it was possible to use tuned or /etc/sysctl.conf to set
> > > these things permanently.
> > >
> > > Given that some people do not want to have debugfs mounted all the time
> > > I would consider this a regression. The sysctl tunable was always
> > > available.
> > >
> > > I am ok with the "informational" things being in debugfs, but not
> > > the tunables. So how do we proceed here?
> >
> > It's all SCHED_DEBUG; IOW you're relying on DEBUG infrastructure for
> > production performance, and that's your fail.
>
> No its not. sched_migration_cost_ns was NEVER protected by CONFIG_SCHED_DEBUG.
> It was available on all kernels with CONFIG_SMP.
The relevant section from origin/master:kernel/sysctl.c:
#ifdef CONFIG_SCHED_DEBUG
{
.procname = "sched_min_granularity_ns",
.data = &sysctl_sched_min_granularity,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sched_proc_update_handler,
.extra1 = &min_sched_granularity_ns,
.extra2 = &max_sched_granularity_ns,
},
{
.procname = "sched_latency_ns",
.data = &sysctl_sched_latency,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sched_proc_update_handler,
.extra1 = &min_sched_granularity_ns,
.extra2 = &max_sched_granularity_ns,
},
{
.procname = "sched_wakeup_granularity_ns",
.data = &sysctl_sched_wakeup_granularity,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sched_proc_update_handler,
.extra1 = &min_wakeup_granularity_ns,
.extra2 = &max_wakeup_granularity_ns,
},
#ifdef CONFIG_SMP
{
.procname = "sched_tunable_scaling",
.data = &sysctl_sched_tunable_scaling,
.maxlen = sizeof(enum sched_tunable_scaling),
.mode = 0644,
.proc_handler = sched_proc_update_handler,
.extra1 = &min_sched_tunable_scaling,
.extra2 = &max_sched_tunable_scaling,
},
{
.procname = "sched_migration_cost_ns",
.data = &sysctl_sched_migration_cost,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "sched_nr_migrate",
.data = &sysctl_sched_nr_migrate,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
#ifdef CONFIG_SCHEDSTATS
{
.procname = "sched_schedstats",
.data = NULL,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sysctl_schedstats,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
#endif /* CONFIG_SCHEDSTATS */
#endif /* CONFIG_SMP */
#ifdef CONFIG_NUMA_BALANCING
{
.procname = "numa_balancing_scan_delay_ms",
.data = &sysctl_numa_balancing_scan_delay,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "numa_balancing_scan_period_min_ms",
.data = &sysctl_numa_balancing_scan_period_min,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "numa_balancing_scan_period_max_ms",
.data = &sysctl_numa_balancing_scan_period_max,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "numa_balancing_scan_size_mb",
.data = &sysctl_numa_balancing_scan_size,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
},
{
.procname = "numa_balancing",
.data = NULL, /* filled in by handler */
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sysctl_numa_balancing,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
How is migration_cost not under SCHED_DEBUG? The bigger problem is that
world+dog has SCHED_DEBUG=y in their .config.
next prev parent reply other threads:[~2021-04-28 9:28 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 10:14 [PATCH v2 0/9] sched: Clean up SCHED_DEBUG Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 1/9] sched/numa: Allow runtime enabling/disabling of NUMA balance without SCHED_DEBUG Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 2/9] sched: Remove sched_schedstats sysctl out from under SCHED_DEBUG Peter Zijlstra
2021-04-16 15:53 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 3/9] sched: Dont make LATENCYTOP select SCHED_DEBUG Peter Zijlstra
2021-04-16 15:53 ` [tip: sched/core] sched: Don't " tip-bot2 for Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 4/9] sched: Move SCHED_DEBUG sysctl to debugfs Peter Zijlstra
2021-04-15 16:29 ` [PATCH] sched/debug: Rename the sched_debug parameter to sched_debug_verbose Peter Zijlstra
2021-04-19 19:26 ` Josh Don
2021-04-16 15:53 ` [tip: sched/core] sched: Move SCHED_DEBUG sysctl to debugfs tip-bot2 for Peter Zijlstra
2021-04-27 14:59 ` Christian Borntraeger
2021-04-27 15:09 ` Steven Rostedt
2021-04-27 15:17 ` Christian Borntraeger
2021-04-28 8:47 ` Peter Zijlstra
2021-04-28 8:46 ` Peter Zijlstra
2021-04-28 8:54 ` Christian Borntraeger
2021-04-28 8:58 ` Christian Borntraeger
2021-04-28 9:25 ` Peter Zijlstra [this message]
2021-04-28 9:31 ` Christian Borntraeger
2021-04-28 9:42 ` Christian Borntraeger
2021-04-28 12:38 ` Peter Zijlstra
2021-04-28 14:49 ` Christian Borntraeger
2021-07-07 12:34 ` [PATCH 0/1] Improve yield (was: sched: Move SCHED_DEBUG sysctl to debugfs) Christian Borntraeger
2021-07-07 12:34 ` [PATCH 1/1] sched/fair: improve yield_to vs fairness Christian Borntraeger
2021-07-07 18:07 ` kernel test robot
2021-07-23 9:35 ` Mel Gorman
2021-07-23 12:36 ` Christian Borntraeger
2021-07-23 16:21 ` Mel Gorman
2021-07-26 18:41 ` Christian Borntraeger
2021-07-26 19:32 ` Mel Gorman
2021-07-27 6:59 ` Christian Borntraeger
2021-07-27 18:57 ` Benjamin Segall
2021-07-28 16:23 ` Christian Borntraeger
2021-08-10 8:49 ` Vincent Guittot
2021-07-27 13:29 ` Peter Zijlstra
2021-07-27 13:33 ` Peter Zijlstra
2021-07-27 14:31 ` Mel Gorman
2021-04-12 10:14 ` [PATCH v2 5/9] sched,preempt: Move preempt_dynamic to debug.c Peter Zijlstra
2021-04-16 15:53 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 6/9] debugfs: Implement debugfs_create_str() Peter Zijlstra
2021-04-16 15:53 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 7/9] sched,debug: Convert sysctl sched_domains to debugfs Peter Zijlstra
2021-04-13 14:55 ` Valentin Schneider
2021-04-15 9:06 ` Peter Zijlstra
2021-04-15 12:16 ` Dietmar Eggemann
2021-04-15 12:34 ` Valentin Schneider
2021-04-15 13:02 ` Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 8/9] sched: Move /proc/sched_debug " Peter Zijlstra
2021-04-16 15:53 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2021-04-12 10:14 ` [PATCH v2 9/9] sched,fair: Alternative sched_slice() Peter Zijlstra
2021-04-12 10:26 ` Peter Zijlstra
2021-04-16 15:53 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
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