Attachment 153515 Details for Bug 197922 – No randomness in scheduler at all

[patch] No randomness in scheduler at all

no_random_in_sched.diff (text/plain), 1.64 KB, created by Harrison Grundy on 2015-02-25 10:40:50 UTC

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Creator: Harrison Grundy

Created: 2015-02-25 10:40:50 UTC

Size: 1.64 KB

patch

obsolete

>Index: sys/kern/sched_ule.c
>===================================================================
>--- sys/kern/sched_ule.c	(revision 278968)
>+++ sys/kern/sched_ule.c	(working copy)
>@@ -277,7 +277,6 @@
> static struct tdq	tdq_cpu[MAXCPU];
> static struct tdq	*balance_tdq;
> static int balance_ticks;
>-static DPCPU_DEFINE(uint32_t, randomval);
> 
> #define	TDQ_SELF()	(&tdq_cpu[PCPU_GET(cpuid)])
> #define	TDQ_CPU(x)	(&tdq_cpu[(x)])
>@@ -651,7 +652,7 @@
> 	cpuset_t cpumask;
> 	struct cpu_group *child;
> 	struct tdq *tdq;
>-	int cpu, i, hload, lload, load, total, rnd, *rndptr;
>+	int cpu, i, hload, lload, load, total;
> 
> 	total = 0;
> 	cpumask = cg->cg_mask;
>@@ -700,9 +701,7 @@
> 			CPU_CLR(cpu, &cpumask);
> 			tdq = TDQ_CPU(cpu);
> 			load = tdq->tdq_load * 256;
>-			rndptr = DPCPU_PTR(randomval);
>-			rnd = (*rndptr = *rndptr * 69069 + 5) >> 26;
>                        if (match & CPU_SEARCH_LOWEST) {
> 				if (cpu == low->cs_prefer)
> 					load -= 64;
> 				/* If that CPU is allowed and get data. */
>@@ -710,7 +709,6 @@
> 				    tdq->tdq_load <= lgroup.cs_limit &&
> 				    CPU_ISSET(cpu, &lgroup.cs_mask)) {
> 					lgroup.cs_cpu = cpu;
>-					lgroup.cs_load = load - rnd;
>+                                       lgroup.cs_load = load;
> 				}
> 			}
> 			if (match & CPU_SEARCH_HIGHEST)
>@@ -861,14 +859,10 @@
> {
> 	struct tdq *tdq;
> 
>-	/*
>-	 * Select a random time between .5 * balance_interval and
>-	 * 1.5 * balance_interval.
>-	 */
>-	balance_ticks = max(balance_interval / 2, 1);
>-	balance_ticks += random() % balance_interval;
> 	if (smp_started == 0 || rebalance == 0)
> 		return;
>+
>+	balance_ticks = balance_interval;
> 	tdq = TDQ_SELF();
> 	TDQ_UNLOCK(tdq);
> 	sched_balance_group(cpu_top);

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Attachments on bug 197922: 153317 | 153415 | 153513 | 153514 | 153515 | 153516