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Subject[PATCH] A nicer nice scheduling
Hi,

please consider including this patch in the main kernel.
It was proposed on 11/04/2001 by Rik van Riel
([test-PATCH] Re: [QUESTION] 2.4.x nice level)

This patch has been working great for me, I applied it to
every new kernel out.

Without this patch, a nice=19 busy-looping process is given
15% of CPU cycles when there is a busy-looping nice=0 process.

Well, if one runs background CPU-consuming programs
(dnetc), this patch makes a nice speed boost.

Please CC to me any replies.

diff -urN linux-2.4.8-lmshsbrnc1/include/linux/sched.h linux-2.4.8-lmshsbrnc1_/include/linux/sched.h
--- linux-2.4.8-lmshsbrnc1/include/linux/sched.h Sun Aug 12 10:18:03 2001
+++ linux-2.4.8-lmshsbrnc1_/include/linux/sched.h Sun Aug 12 12:19:16 2001
@@ -305,7 +305,8 @@
* the goodness() loop in schedule().
*/
long counter;
- long nice;
+ short nice_calc;
+ short nice;
unsigned long policy;
struct mm_struct *mm;
int has_cpu, processor;
diff -urN linux-2.4.8-lmshsbrnc1/kernel/sched.c linux-2.4.8-lmshsbrnc1_/kernel/sched.c
--- linux-2.4.8-lmshsbrnc1/kernel/sched.c Sun Aug 12 10:18:03 2001
+++ linux-2.4.8-lmshsbrnc1_/kernel/sched.c Sun Aug 12 12:19:16 2001
@@ -680,8 +680,26 @@
struct task_struct *p;
spin_unlock_irq(&runqueue_lock);
read_lock(&tasklist_lock);
- for_each_task(p)
+ for_each_task(p) {
+ if (p->nice <= 0) {
+ /* The normal case... */
p->counter = (p->counter >> 1) + NICE_TO_TICKS(p->nice);
+ } else {
+ /*
+ * Niced tasks get less CPU less often, leading to
+ * the following distribution of CPU time:
+ *
+ * Nice 0 5 10 15 19
+ * %CPU 100 56 25 6 1
+ */
+ short prio = 20 - p->nice;
+ p->nice_calc += prio;
+ if (p->nice_calc >= 20) {
+ p->nice_calc -= 20;
+ p->counter = (p->counter >> 1) + NICE_TO_TICKS(p->nice);
+ }
+ }
+ }
read_unlock(&tasklist_lock);
spin_lock_irq(&runqueue_lock);
}

--
Roberto Ragusa robertoragusa at technologist.com

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