Re: dynamic sched timeslices

[Kurt Garloff]

Hi Christoph,

quick response!
On Mon, Mar 15, 2004 at 10:59:39PM +0000, Christoph Hellwig wrote:
> Remove the silly desktop boot parameter and the patch looks basically
> okay to me.

See attachment.

> I remember we had a more complete patch to allow tuning the scheduler
> through sysctls in -mm once, though.  Questions is why that one wasn't
> merged and if the same reasons apply to a 'light' version.

Hmm, I fail to remember unfortunately. Probably it had too many knobs.
Andrew?

Regards,
-- 
Kurt Garloff  <garloff@xxxxxxx>                            Cologne, DE 
SUSE LINUX AG, Nuernberg, DE                          SUSE Labs (Head)
diff -uNr linux-2.6.4/include/linux/sched.h linux-2.6.4.dyn-timeslice/include/linux/sched.h
--- linux-2.6.4/include/linux/sched.h	2004-03-16 00:03:52.000000000 +0100
+++ linux-2.6.4.dyn-timeslice/include/linux/sched.h	2004-03-16 00:05:14.000000000 +0100
@@ -176,6 +176,7 @@
 #define	MAX_SCHEDULE_TIMEOUT	LONG_MAX
 extern signed long FASTCALL(schedule_timeout(signed long timeout));
 asmlinkage void schedule(void);
+extern int max_timeslice, min_timeslice;
 
 struct namespace;
 
diff -uNr linux-2.6.4/include/linux/sysctl.h linux-2.6.4.dyn-timeslice/include/linux/sysctl.h
--- linux-2.6.4/include/linux/sysctl.h	2004-03-16 00:03:52.000000000 +0100
+++ linux-2.6.4.dyn-timeslice/include/linux/sysctl.h	2004-03-16 00:07:31.000000000 +0100
@@ -134,6 +134,9 @@
 	KERN_KDB=64,		/* int: kdb on/off */
 	KERN_S390_HZ_TIMER=65,  /* int: hz timer on or off */
 	KERN_DUMP=66,		/* directory: dump parameters */
+	KERN_MAXTIMESLICE=67,	/* int: nice -20 max timeslice */
+	KERN_MINTIMESLICE=68,	/* int: nice +19 min timeslice */
+	KERN_HZ=69,		/* unsigned long: internal kernel HZ */
 };
 
 
diff -uNr linux-2.6.4/kernel/sched.c linux-2.6.4.dyn-timeslice/kernel/sched.c
--- linux-2.6.4/kernel/sched.c	2004-03-16 00:03:52.000000000 +0100
+++ linux-2.6.4.dyn-timeslice/kernel/sched.c	2004-03-16 00:06:14.000000000 +0100
@@ -79,12 +79,17 @@
 /*
  * These are the 'tuning knobs' of the scheduler:
  *
- * Minimum timeslice is 10 msecs, default timeslice is 100 msecs,
- * maximum timeslice is 200 msecs. Timeslices get refilled after
- * they expire.
- */
-#define MIN_TIMESLICE		( 10 * HZ / 1000)
-#define MAX_TIMESLICE		(200 * HZ / 1000)
+ * Minimum timeslice is 10 msecs, default timeslice is 150 msecs,
+ * maximum timeslice is 300 msecs. Timeslices get refilled after
+ * they expire. 
+ */
+#define __MIN_TIMESLICE		  10000
+#define __MAX_TIMESLICE		 300000
+/* the sysctl values are exported in usec units to userspace */
+int max_timeslice = __MAX_TIMESLICE, min_timeslice = __MIN_TIMESLICE;
+#define MAX_TIMESLICE ((max_timeslice * HZ + 999999) / 1000000)
+#define MIN_TIMESLICE ((min_timeslice * HZ + 999999) / 1000000)
+
 #define ON_RUNQUEUE_WEIGHT	 30
 #define CHILD_PENALTY		 95
 #define PARENT_PENALTY		100
diff -uNr linux-2.6.4/kernel/sysctl.c linux-2.6.4.dyn-timeslice/kernel/sysctl.c
--- linux-2.6.4/kernel/sysctl.c	2004-03-16 00:03:52.000000000 +0100
+++ linux-2.6.4.dyn-timeslice/kernel/sysctl.c	2004-03-16 00:05:14.000000000 +0100
@@ -167,6 +167,7 @@
 static void unregister_proc_table(ctl_table *, struct proc_dir_entry *);
 #endif
 
+static unsigned long __HZ = HZ;
 /* The default sysctl tables: */
 
 static ctl_table root_table[] = {
@@ -642,6 +643,30 @@
 		.mode		= 0444,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= KERN_MAXTIMESLICE, 
+		.procname	= "max-timeslice",
+		.data		=  &max_timeslice,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
+		.ctl_name	= KERN_MINTIMESLICE, 
+		.procname	= "min-timeslice",
+		.data		= &min_timeslice,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
+		.ctl_name	= KERN_HZ, 
+		.procname	= "HZ",
+		.data		= &__HZ,
+		.maxlen		= sizeof(long),
+		.mode		= 0444,
+		.proc_handler	= &proc_dointvec,
+	},
 	{ .ctl_name = 0 }
 };

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