/proc/sys/kernel/cache_decay_ticks allows runtime tuning of the
scheduler. The earlier patch collided with the C99-ification of the
file, so here is a retransmit.
--david
diff -Nru a/include/linux/sysctl.h b/include/linux/sysctl.h
--- a/include/linux/sysctl.h Wed Jun 18 13:32:49 2003
+++ b/include/linux/sysctl.h Wed Jun 18 13:32:49 2003
@@ -130,6 +130,7 @@
KERN_PIDMAX=55, /* int: PID # limit */
KERN_CORE_PATTERN=56, /* string: pattern for core-file names */
KERN_PANIC_ON_OOPS=57, /* int: whether we will panic on an oops */
+ KERN_CACHEDECAYTICKS=58, /* ulong: value for cache_decay_ticks (EXPERIMENTAL!) */
};
diff -Nru a/kernel/sysctl.c b/kernel/sysctl.c
--- a/kernel/sysctl.c Wed Jun 18 13:32:49 2003
+++ b/kernel/sysctl.c Wed Jun 18 13:32:49 2003
@@ -551,6 +551,16 @@
.mode = 0644,
.proc_handler = &proc_dointvec,
},
+#ifdef CONFIG_SMP
+ {
+ .ctl_name = KERN_CACHEDECAYTICKS,
+ .procname = "cache_decay_ticks",
+ .data = &cache_decay_ticks,
+ .maxlen = sizeof(cache_decay_ticks),
+ .mode = 0644,
+ .proc_handler = &proc_doulongvec_minmax,
+ },
+#endif
{ .ctl_name = 0 }
};
David Mosberger <[email protected]> writes:
> /proc/sys/kernel/cache_decay_ticks allows runtime tuning of the
> scheduler. The earlier patch collided with the C99-ification of the
> file, so here is a retransmit.
Funny, I did a similar patch for 2.4 a short time ago. But I would
suggest one change before you merge that to mainline. The variable
is currently used like this:
#define CAN_MIGRATE_TASK(p,rq,this_cpu) \
((jiffies - (p)->last_run > cache_decay_ticks) && \o
Which means 0 means 1 jiffie. For a tunable it would be useful to be
able to turn it off completely, which means the > needs to be replaced
with a >=. Unfortunately this requires changes in the architectures
too to subtract one. But it would make it more useful. I would do
the change before exposing it.
-Andi
>>>>> On 19 Jun 2003 00:05:18 +0200, Andi Kleen <[email protected]> said:
Andi> David Mosberger <[email protected]> writes:
>> /proc/sys/kernel/cache_decay_ticks allows runtime tuning of the
>> scheduler. The earlier patch collided with the C99-ification of
>> the file, so here is a retransmit.
Andi> Funny, I did a similar patch for 2.4 a short time ago. But I
Andi> would suggest one change before you merge that to
Andi> mainline. The variable is currently used like this:
Andi> #define CAN_MIGRATE_TASK(p,rq,this_cpu) \ ((jiffies -
Andi> (p)->last_run > cache_decay_ticks) && \o
Andi> Which means 0 means 1 jiffie. For a tunable it would be useful
Andi> to be able to turn it off completely, which means the > needs
Andi> to be replaced with a >=. Unfortunately this requires changes
Andi> in the architectures too to subtract one. But it would make it
Andi> more useful. I would do the change before exposing it.
I don't see why the two have to be tied together. I agree it would be
_nice_, but having /proc/sys/kernel/cache_decay_ticks in it's current
form is much better than nothing at all.
--david
> I don't see why the two have to be tied together. I agree it would be
> _nice_, but having /proc/sys/kernel/cache_decay_ticks in it's current
> form is much better than nothing at all.
The problem is that when you change it later with the sysctl you have a subtle
user visible change, breaking existing users.
-Andi