[PATCH] nitro: make multiplier scaleable, change "nitro_hzmultiplicator" into "nitro_hz_permille"

Stephan Bärwolf
2012-02-28T10:55:14Z

This patch extends the conventional "nitro_hzmultiplicator" into a permille-base.
So now it is possible also to scale down HZ. (For example half HZ would be possible
with nitro_hz_permille=500, a quarter nitro_hz_permille=250 ...etc...)
As always, jiffies_64 increases with HZ frequency.

The new proc-file is called "nitro_hz_permille"
The new config-option is called "CONFIG_SCHED_NITRO_HZBOOST_PERMILLE"

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
---
kernel/Kconfig.sched | 17 +++++++++--------
kernel/sysctl.c | 12 ++++++------
kernel/time/tick-common.c | 14 +++++++-------
kernel/time/tick-internal.h | 19 ++++++++++++++-----
4 files changed, 36 insertions(+), 26 deletions(-)

diff --git a/kernel/Kconfig.sched b/kernel/Kconfig.sched
index 27e5518..a066434 100644
--- a/kernel/Kconfig.sched
+++ b/kernel/Kconfig.sched
@@ -176,23 +176,24 @@ config SCHED_NITRO_HZBOOST_USERSPAC
accessable from userspace via procfs.
The responsible file will be called /proc/sys/kernel/nitro_hzmultiplicator

-config SCHED_NITRO_HZBOOST_MULTIPLICATOR
- int "Multiply the HZ frequency value"
- range 1 100
- default 1
+config SCHED_NITRO_HZBOOST_PERMILLE
+ int "Skale the HZ frequency value (per mille)"
+ range 1 100000
+ default 1000
depends on (SCHED_NITRO_HZBOOST && X86_64 && SCHED_HRTICK)
help
Normally the scheduler code (scheduler_tick()) ticks with "HZ" frequency.
With this frequency also "jiffies_64" is increased and is used by
timerelated kernelcode.
- This Option increases the schedulers tickerfrequency by multiplying
- this multiplicator with HZ. However the jiffies_64 is STILL updated
- with HZ-frequency and all the jiffy-based timecode is working further on.
+ This Option skales the schedulers tickerfrequency by multiplying
+ this per-mille value with HZ (and divides everything by 1000).
+ However the jiffies_64 is STILL updated with HZ-frequency and all the
+ jiffy-based timecode is working further on.

Asyncron ns-time-based code will take advantage from this option and
scheduling will become finer and more interactive.

- WARNING: !! THIS OPTION WILL INCREASE YOUR "INTERRUPTS PER SECOND" FOR
+ WARNING: !! THIS OPTION MAY INCREASE YOUR "INTERRUPTS PER SECOND" FOR
EACH ONLINE CPU. THIS WILL ALSO INCREASE YOUR SYSTEMOVERHEAD !!
endmenu

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6c95dfe..f8cec40 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -253,8 +253,8 @@ static struct ctl_table root_table[] = {

#ifdef CONFIG_SCHED_NITRO_HZBOOST_USERSPAC
#include "time/tick-internal.h"
-static int min_tick_period_HZmultiplicator = 1;
-static int max_tick_period_HZmultiplicator = 100;
+static int min_tick_period_HZscalepermille = 1;
+static int max_tick_period_HZscalepermille = 100000;
#endif
#ifdef CONFIG_SCHED_DEBUG
static int min_sched_granularity_ns = 100000; /* 100 usecs */
@@ -280,13 +280,13 @@ static struct ctl_table kern_table[] = {
},
#ifdef CONFIG_SCHED_NITRO_HZBOOST_USERSPAC
{
- .procname = "nitro_hzmultiplicator",
- .data = &sysctl_tick_period_HZmultiplicator,
+ .procname = "nitro_hz_permille",
+ .data = &sysctl_tick_period_HZscalepermille,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = tick_change_periodmultiplicator_handler,
- .extra1 = &min_tick_period_HZmultiplicator,
- .extra2 = &max_tick_period_HZmultiplicator,
+ .extra1 = &min_tick_period_HZscalepermille,
+ .extra2 = &max_tick_period_HZscalepermille,
},
#endif
#ifdef CONFIG_SCHED_DEBUG
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 1c62de8..a0176e245 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -170,7 +170,7 @@ static void tick_setup_device(struct tick_device *td,
tick_next_period = ktime_get();
#ifdef CONFIG_SCHED_NITRO_HZBOOST
tick_HZbaseperiod = ktime_set(0, NSEC_PER_SEC / HZ);
- tick_change_periodmultiplicator(CONFIG_SCHED_NITRO_HZBOOST_MULTIPLICATOR);
+ tick_change_periodmultiplicator(CONFIG_SCHED_NITRO_HZBOOST_PERMILLE);
#else
tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
#endif
@@ -427,8 +427,8 @@ void __init tick_init(void)
}

#ifdef CONFIG_SCHED_NITRO_HZBOOST_USERSPAC
-unsigned int sysctl_tick_period_HZmultiplicator = ((unsigned long)CONFIG_SCHED_NITRO_HZBOOST_MULTIPLICATOR);
-static unsigned int __last_HZmultiplicator = ((unsigned long)CONFIG_SCHED_NITRO_HZBOOST_MULTIPLICATOR);
+unsigned int sysctl_tick_period_HZscalepermille = ((unsigned long)CONFIG_SCHED_NITRO_HZBOOST_PERMILLE);
+static unsigned int __last_HZscalepermille = ((unsigned long)CONFIG_SCHED_NITRO_HZBOOST_PERMILLE);

int tick_change_periodmultiplicator_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
@@ -439,11 +439,11 @@ int tick_change_periodmultiplicator_handler(struct ctl_table *table, int write,
if (ret || !write)
return ret;

- if (sysctl_tick_period_HZmultiplicator > 0)
- if (__last_HZmultiplicator != sysctl_tick_period_HZmultiplicator) {
+ if (sysctl_tick_period_HZscalepermille > 0)
+ if (__last_HZscalepermille != sysctl_tick_period_HZscalepermille) {
write_seqlock(&xtime_lock);
- tick_change_periodmultiplicator(sysctl_tick_period_HZmultiplicator);
- __last_HZmultiplicator = sysctl_tick_period_HZmultiplicator;
+ tick_change_periodmultiplicator(sysctl_tick_period_HZscalepermille);
+ __last_HZscalepermille = sysctl_tick_period_HZscalepermille;
write_sequnlock(&xtime_lock);
}

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index eb60d32..26a1bda 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -17,19 +17,28 @@ extern int tick_do_timer_cpu __read_mostly;
#ifdef CONFIG_SCHED_NITRO_HZBOOST
extern ktime_t tick_HZbaseperiod;
#ifdef CONFIG_SCHED_NITRO_HZBOOST_USERSPAC
-extern unsigned int sysctl_tick_period_HZmultiplicator;
+extern unsigned int sysctl_tick_period_HZscalepermille;
extern int tick_change_periodmultiplicator_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos);
#endif
/*
* proper locking has to be taken care outside
+ *
+ * scalepermille better be not zero!
+ *
*/
-static inline void tick_change_periodmultiplicator(const unsigned long long multiplicator)
+static inline void tick_change_periodmultiplicator(const unsigned long long scalepermille)
{
- printk( KERN_NOTICE "changing nitro hzboost multiplicator, new frequency: %llu x %lluHz\n", multiplicator, (unsigned long long)HZ);
- tick_period = ktime_set(0, NSEC_PER_SEC / (HZ*multiplicator));
- printk( KERN_NOTICE "scheduler nitro-patchset v1.0 Ilmenau 2012, by Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>\n");
+ unsigned long long __nanoseconds = (((unsigned long long)NSEC_PER_SEC) * 1000ULL) / scalepermille;
+ unsigned int i,j;
+
+ i = scalepermille / 1000;
+ j = scalepermille % 1000;
+
+ printk( KERN_NOTICE "changing nitro hzboost multiplicator, new frequency: %u.%03u x %lluHz\n", i, j, (unsigned long long)HZ);
+ tick_period = ktime_set(0, __nanoseconds / ((unsigned long long)HZ));
+ printk( KERN_NOTICE "scheduler nitro-patchset v1.0.1 Ilmenau 2012, by Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>\n");
}
#endif

--
1.7.3.4