[Patch 2/7] Add sysctl for schedstats

schedstats-sysctl.patch

Add sysctl option for controlling schedstats collection
dynamically. Delay accounting leverages schedstats for
cpu delay statistics.

Signed-off-by: Chandra Seetharaman <sekharan@xxxxxxxxxx>
Signed-off-by: Shailabh Nagar <nagar@xxxxxxxxxxxxxx>

Documentation/kernel-parameters.txt | 2
include/linux/sched.h | 4 +
include/linux/sysctl.h | 1
kernel/sched.c | 74 +++++++++++++++++++++++++++++++++---
kernel/sysctl.c | 10 ++++
lib/Kconfig.debug | 6 +-
6 files changed, 90 insertions(+), 7 deletions(-)

Index: linux-2.6.16-rc4/include/linux/sched.h
===================================================================
--- linux-2.6.16-rc4.orig/include/linux/sched.h 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/include/linux/sched.h 2006-02-27 01:52:52.000000000 -0500
@@ -15,6 +15,7 @@
#include <linux/cpumask.h>
#include <linux/errno.h>
#include <linux/nodemask.h>
+#include <linux/sysctl.h>

#include <asm/system.h>
#include <asm/semaphore.h>
@@ -525,6 +526,9 @@ struct backing_dev_info;
struct reclaim_state;

#ifdef CONFIG_SCHEDSTATS
+extern int schedstats_sysctl;
+extern int schedstats_sysctl_handler(ctl_table *, int, struct file *,
+ void __user *, size_t *, loff_t *);
struct sched_info {
/* cumulative counters */
unsigned long cpu_time, /* time spent on the cpu */
Index: linux-2.6.16-rc4/include/linux/sysctl.h
===================================================================
--- linux-2.6.16-rc4.orig/include/linux/sysctl.h 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/include/linux/sysctl.h 2006-02-27 01:52:52.000000000 -0500
@@ -146,6 +146,7 @@ enum
KERN_RANDOMIZE=68, /* int: randomize virtual address space */
KERN_SETUID_DUMPABLE=69, /* int: behaviour of dumps for setuid core */
KERN_SPIN_RETRY=70, /* int: number of spinlock retries */
+ KERN_SCHEDSTATS=71, /* int: Schedstats on/off */
};


Index: linux-2.6.16-rc4/kernel/sched.c
===================================================================
--- linux-2.6.16-rc4.orig/kernel/sched.c 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/kernel/sched.c 2006-02-27 01:52:52.000000000 -0500
@@ -382,11 +382,56 @@ static inline void task_rq_unlock(runque
}

#ifdef CONFIG_SCHEDSTATS
+
+int schedstats_sysctl = 0; /* schedstats turned off by default */
+static DEFINE_PER_CPU(int, schedstats) = 0;
+
+static void schedstats_set(int val)
+{
+ int i;
+ static spinlock_t schedstats_lock = SPIN_LOCK_UNLOCKED;
+
+ spin_lock(&schedstats_lock);
+ schedstats_sysctl = val;
+ for (i = 0; i < NR_CPUS; i++)
+ per_cpu(schedstats, i) = val;
+ spin_unlock(&schedstats_lock);
+}
+
+static int __init schedstats_setup_enable(char *str)
+{
+ schedstats_sysctl = 1;
+ schedstats_set(schedstats_sysctl);
+ return 1;
+}
+
+__setup("schedstats", schedstats_setup_enable);
+
+int schedstats_sysctl_handler(ctl_table *table, int write, struct file *filp,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ int ret, prev = schedstats_sysctl;
+ struct task_struct *g, *t;
+
+ ret = proc_dointvec(table, write, filp, buffer, lenp, ppos);
+ if ((ret != 0) || (prev == schedstats_sysctl))
+ return ret;
+ if (schedstats_sysctl) {
+ read_lock(&tasklist_lock);
+ do_each_thread(g, t) {
+ memset(&t->sched_info, 0, sizeof(t->sched_info));
+ } while_each_thread(g, t);
+ read_unlock(&tasklist_lock);
+ }
+ schedstats_set(schedstats_sysctl);
+ return ret;
+}
+
/*
* bump this up when changing the output format or the meaning of an existing
* format, so that tools can adapt (or abort)
*/
-#define SCHEDSTAT_VERSION 12
+#define SCHEDSTAT_VERSION 13

static int show_schedstat(struct seq_file *seq, void *v)
{
@@ -394,6 +439,10 @@ static int show_schedstat(struct seq_fil

seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
seq_printf(seq, "timestamp %lu\n", jiffies);
+ if (!schedstats_sysctl) {
+ seq_printf(seq, "State Off\n");
+ return 0;
+ }
for_each_online_cpu(cpu) {
runqueue_t *rq = cpu_rq(cpu);
#ifdef CONFIG_SMP
@@ -472,8 +521,17 @@ struct file_operations proc_schedstat_op
.release = single_release,
};

-# define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
-# define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
+#define schedstats_on (per_cpu(schedstats, smp_processor_id()) != 0)
+#define schedstat_inc(rq, field) \
+do { \
+ if (unlikely(schedstats_on)) \
+ (rq)->field++; \
+} while (0)
+#define schedstat_add(rq, field, amt) \
+do { \
+ if (unlikely(schedstats_on)) \
+ (rq)->field += (amt); \
+} while (0)
#else /* !CONFIG_SCHEDSTATS */
# define schedstat_inc(rq, field) do { } while (0)
# define schedstat_add(rq, field, amt) do { } while (0)
@@ -556,7 +614,7 @@ static void sched_info_arrive(task_t *t)
*/
static inline void sched_info_queued(task_t *t)
{
- if (!t->sched_info.last_queued)
+ if (unlikely(schedstats_on && !t->sched_info.last_queued))
t->sched_info.last_queued = jiffies;
}

@@ -580,7 +638,7 @@ static inline void sched_info_depart(tas
* their time slice. (This may also be called when switching to or from
* the idle task.) We are only called when prev != next.
*/
-static inline void sched_info_switch(task_t *prev, task_t *next)
+static inline void __sched_info_switch(task_t *prev, task_t *next)
{
struct runqueue *rq = task_rq(prev);

@@ -595,6 +653,12 @@ static inline void sched_info_switch(tas
if (next != rq->idle)
sched_info_arrive(next);
}
+
+static inline void sched_info_switch(task_t *prev, task_t *next)
+{
+ if (unlikely(schedstats_on))
+ __sched_info_switch(prev, next);
+}
#else
#define sched_info_queued(t) do { } while (0)
#define sched_info_switch(t, next) do { } while (0)
Index: linux-2.6.16-rc4/kernel/sysctl.c
===================================================================
--- linux-2.6.16-rc4.orig/kernel/sysctl.c 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/kernel/sysctl.c 2006-02-27 01:52:52.000000000 -0500
@@ -656,6 +656,16 @@ static ctl_table kern_table[] = {
.proc_handler = &proc_dointvec,
},
#endif
+#if defined(CONFIG_SCHEDSTATS)
+ {
+ .ctl_name = KERN_SCHEDSTATS,
+ .procname = "schedstats",
+ .data = &schedstats_sysctl,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &schedstats_sysctl_handler,
+ },
+#endif
{ .ctl_name = 0 }
};

Index: linux-2.6.16-rc4/lib/Kconfig.debug
===================================================================
--- linux-2.6.16-rc4.orig/lib/Kconfig.debug 2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/lib/Kconfig.debug 2006-02-27 01:52:52.000000000 -0500
@@ -67,15 +67,17 @@ config DETECT_SOFTLOCKUP

config SCHEDSTATS
bool "Collect scheduler statistics"
- depends on DEBUG_KERNEL && PROC_FS
+ depends on PROC_FS
help
If you say Y here, additional code will be inserted into the
scheduler and related routines to collect statistics about
scheduler behavior and provide them in /proc/schedstat. These
- stats may be useful for both tuning and debugging the scheduler
+ stats may be useful for both tuning and debugging the scheduler.
If you aren't debugging the scheduler or trying to tune a specific
application, you can say N to avoid the very slight overhead
this adds.
+ Schedstats collection, and most of its overhead, can also be
+ controlled dyanmically through the schedstats sysctl.

config DEBUG_SLAB
bool "Debug memory allocations"
Index: linux-2.6.16-rc4/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.16-rc4.orig/Documentation/kernel-parameters.txt 2006-02-27 01:19:52.000000000 -0500
+++ linux-2.6.16-rc4/Documentation/kernel-parameters.txt 2006-02-27 01:52:52.000000000 -0500
@@ -1333,6 +1333,8 @@ running once the system is up.
sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
Format: <io>[,<timeout>[,<isapnp>]]

+ schedstats [KNL] Collect CPU scheduler statistics
+
scsi_debug_*= [SCSI]
See drivers/scsi/scsi_debug.c.



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages

  • schedstats refinement (was Re: [Lse-tech] Re: [Patch 2/7] Add sysctl for schedstats)
    ... Add sysctl option for controlling schedstats collection ... This patch refines scheduler statistics collection and display to three levels, ... added (for each cpu) to the /proc/schedstat output. ... goto out_set_cpu; ...
    (Linux-Kernel)
  • Re: 2.6.9-rc1-mm1
    ... > Rick's schedstats stuff had some ways to measure latency that seemed to ... contains the Nick's scheduler (2.6.9-rc1 has the same scheduler as 2.6.8.1, ... send the line "unsubscribe linux-kernel" in ...
    (Linux-Kernel)
  • 2.6 Kernel statistics collection
    ... kernel statistics in the following areas, ... (Something which can give scheduler ... send the line "unsubscribe linux-kernel" in ...
    (Linux-Kernel)
  • Re: Doubt about scheduler
    ... to make a final degree job, and mine is about modules in linux, I would like to show information of the new scheduler, a scheduler monitor, and these fields are indispensable for me) ... if you want a scheduler monitor then I can't see ... why it would be appropriate to implement as a module (we have schedstats, ...
    (Linux-Kernel)
  • Re: The duration of one single oracle job
    ... I user Oracle 10g, but we do not use the scheduler, but dbms_jobs. ... I have a job that gathers table statistics once a week. ... I want to know how long the last job execution took. ...
    (comp.databases.oracle.server)