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From: Peter Zijlstra <peterz@infradead.org>
To: tglx@linutronix.de, mingo@kernel.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
	bristot@redhat.com, bsingharora@gmail.com, pbonzini@redhat.com,
	maz@kernel.org
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	riel@surriel.com, hannes@cmpxchg.org
Subject: [PATCH 7/6] delayacct: Add sysctl to enable at runtime
Date: Mon, 10 May 2021 14:05:13 +0200	[thread overview]
Message-ID: <YJkhebGJAywaZowX@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210505105940.190490250@infradead.org>


Just like sched_schedstats, allow runtime enabling (and disabling) of
delayacct. This is useful if one forgot to add the delayacct boot time
option.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 Documentation/accounting/delay-accounting.rst |    6 ++--
 kernel/delayacct.c                            |   36 ++++++++++++++++++++++++--
 kernel/sysctl.c                               |   12 ++++++++
 3 files changed, 50 insertions(+), 4 deletions(-)

--- a/Documentation/accounting/delay-accounting.rst
+++ b/Documentation/accounting/delay-accounting.rst
@@ -74,8 +74,10 @@ Delay accounting is disabled by default
 
    delayacct
 
-to the kernel boot options. The rest of the instructions
-below assume this has been done.
+to the kernel boot options. The rest of the instructions below assume this has
+been done. Alternatively, use sysctl kernel.sched_delayacct to switch the state
+at runtime. Note however that only tasks started after enabling it will have
+delayacct information.
 
 After the system has booted up, use a utility
 similar to  getdelays.c to access the delays
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -18,6 +18,17 @@ DEFINE_STATIC_KEY_FALSE(delayacct_key);
 int delayacct_on __read_mostly;	/* Delay accounting turned on/off */
 struct kmem_cache *delayacct_cache;
 
+static void set_delayacct(bool enabled)
+{
+	if (enabled) {
+		static_branch_enable(&delayacct_key);
+		delayacct_on = 1;
+	} else {
+		delayacct_on = 0;
+		static_branch_disable(&delayacct_key);
+	}
+}
+
 static int __init delayacct_setup_enable(char *str)
 {
 	delayacct_on = 1;
@@ -29,9 +40,30 @@ void delayacct_init(void)
 {
 	delayacct_cache = KMEM_CACHE(task_delay_info, SLAB_PANIC|SLAB_ACCOUNT);
 	delayacct_tsk_init(&init_task);
-	if (delayacct_on)
-		static_branch_enable(&delayacct_key);
+	set_delayacct(delayacct_on);
+}
+
+#ifdef CONFIG_PROC_SYSCTL
+int sysctl_delayacct(struct ctl_table *table, int write, void *buffer,
+		     size_t *lenp, loff_t *ppos)
+{
+	int state = delayacct_on;
+	struct ctl_table t;
+	int err;
+
+	if (write && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	t = *table;
+	t.data = &state;
+	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+	if (err < 0)
+		return err;
+	if (write)
+		set_delayacct(state);
+	return err;
 }
+#endif
 
 void __delayacct_tsk_init(struct task_struct *tsk)
 {
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -71,6 +71,7 @@
 #include <linux/coredump.h>
 #include <linux/latencytop.h>
 #include <linux/pid.h>
+#include <linux/delayacct.h>
 
 #include "../lib/kstrtox.h"
 
@@ -1727,6 +1728,17 @@ static struct ctl_table kern_table[] = {
 		.extra2		= SYSCTL_ONE,
 	},
 #endif /* CONFIG_SCHEDSTATS */
+#ifdef CONFIG_TASK_DELAY_ACCT
+	{
+		.procname	= "sched_delayacct",
+		.data		= NULL,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= sysctl_delayacct,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+#endif /* CONFIG_TASK_DELAY_ACCT */
 #ifdef CONFIG_NUMA_BALANCING
 	{
 		.procname	= "numa_balancing",

  parent reply	other threads:[~2021-05-10 13:02 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05 10:59 [PATCH 0/6] sched,delayacct: Some cleanups Peter Zijlstra
2021-05-05 10:59 ` [PATCH 1/6] delayacct: Use sched_clock() Peter Zijlstra
2021-05-05 14:40   ` Rik van Riel
2021-05-06 13:59   ` Johannes Weiner
2021-05-06 14:17     ` Peter Zijlstra
2021-05-06 15:17       ` Johannes Weiner
2021-05-07 12:40   ` Balbir Singh
2021-05-12 10:43   ` Mel Gorman
2021-05-05 10:59 ` [PATCH 2/6] sched: Rename sched_info_{queued,dequeued} Peter Zijlstra
2021-05-05 14:39   ` Rik van Riel
2021-05-06 13:59   ` Johannes Weiner
2021-05-10  8:45   ` Balbir Singh
2021-05-12 10:49   ` Mel Gorman
2021-05-05 10:59 ` [PATCH 3/6] sched: Simplify sched_info_on() Peter Zijlstra
2021-05-06 14:03   ` Johannes Weiner
2021-05-12 11:10   ` Mel Gorman
2021-05-12 11:32     ` Peter Zijlstra
2021-05-12 12:51       ` Mel Gorman
2021-05-05 10:59 ` [PATCH 4/6] kvm: Select SCHED_INFO instead of TASK_DELAY_ACCT Peter Zijlstra
2021-05-05 11:37   ` Paolo Bonzini
2021-05-06 14:38   ` Marc Zyngier
2021-05-07 12:42   ` Balbir Singh
2021-05-12 11:11   ` Mel Gorman
2021-05-05 10:59 ` [PATCH 5/6] delayacct: Add static_branch in scheduler hooks Peter Zijlstra
2021-05-06 14:05   ` Johannes Weiner
2021-05-10  8:42   ` Balbir Singh
2021-05-12 11:13   ` Mel Gorman
2021-05-05 10:59 ` [PATCH 6/6] [RFC] delayacct: Default disabled Peter Zijlstra
2021-05-12 11:35   ` Mel Gorman
2021-05-05 22:29 ` [PATCH 0/6] sched,delayacct: Some cleanups Balbir Singh
2021-05-06  9:13   ` Peter Zijlstra
2021-05-07 12:38     ` Balbir Singh
2021-05-12 11:34       ` Mel Gorman
2021-05-12 11:38         ` Peter Zijlstra
2021-05-12 12:23         ` Paul Wise
2021-05-12 13:00           ` Mel Gorman
2021-05-13  1:29             ` Paul Wise
2021-06-25  0:50         ` Paul Wise
2021-05-07  9:05 ` Thomas Gleixner
2021-05-10  7:08 ` Ingo Molnar
2021-05-10 12:05 ` Peter Zijlstra [this message]
2021-05-10 12:06   ` [PATCH 7/6] delayacct: Add sysctl to enable at runtime Peter Zijlstra
2021-05-12 11:40   ` Mel Gorman

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