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Subjectadd lowpower_idle sysctl
Date
On ia64, we need runtime control to manage CPU power state in the idle
loop. Logically it means a sysctl entry in /proc/sys/kernel. Even
though this sysctl entry doesn't exist today, lots of arch already has
some sort of API to dynamically enable/disable low power idle state.
Looking at linux-2.6.4, arm, arm26, cris, i386, parisc, sh, um, x86-64
all has very much the same code in each arch. So instead of replicate
another set under arch/ia64, we are proposing these API to be abstracted
out in the generic code. And also add a sysctl entry under /proc/sys/kernel.

Would this be useful to all architecture who wants this features? It
would be a lot less code duplication.

- Ken


diff -Nur linux-2.6.4/include/linux/sysctl.h linux-2.6.4.halt/include/linux/sysctl.h
--- linux-2.6.4/include/linux/sysctl.h 2004-03-10 18:55:28.000000000 -0800
+++ linux-2.6.4.halt/include/linux/sysctl.h 2004-03-17 15:33:30.000000000 -0800
@@ -131,6 +131,7 @@
KERN_PRINTK_RATELIMIT_BURST=61, /* int: tune printk ratelimiting */
KERN_PTY=62, /* dir: pty driver */
KERN_NGROUPS_MAX=63, /* int: NGROUPS_MAX */
+ KERN_LOWPOWER_IDLE=64, /* int: low power idle */
};


diff -Nur linux-2.6.4/kernel/cpu.c linux-2.6.4.halt/kernel/cpu.c
--- linux-2.6.4/kernel/cpu.c 2004-03-10 18:55:44.000000000 -0800
+++ linux-2.6.4.halt/kernel/cpu.c 2004-03-17 15:36:32.000000000 -0800
@@ -64,3 +64,15 @@
up(&cpucontrol);
return ret;
}
+
+atomic_t halt_counter;
+void enable_halt(void)
+{
+ atomic_dec(&halt_counter);
+}
+void disable_halt(void)
+{
+ atomic_inc(&halt_counter);
+}
+EXPORT_SYMBOL(enable_halt);
+EXPORT_SYMBOL(disable_halt);
diff -Nur linux-2.6.4/kernel/sysctl.c linux-2.6.4.halt/kernel/sysctl.c
--- linux-2.6.4/kernel/sysctl.c 2004-03-10 18:55:22.000000000 -0800
+++ linux-2.6.4.halt/kernel/sysctl.c 2004-03-17 15:34:52.000000000 -0800
@@ -64,6 +64,7 @@
extern int min_free_kbytes;
extern int printk_ratelimit_jiffies;
extern int printk_ratelimit_burst;
+extern atomic_t halt_counter;

/* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
static int maxolduid = 65535;
@@ -615,6 +616,14 @@
.mode = 0444,
.proc_handler = &proc_dointvec,
},
+ {
+ .ctl_name = KERN_LOWPOWER_IDLE,
+ .procname = "lowpower_idle",
+ .data = &halt_counter,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
{ .ctl_name = 0 }
};


-
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