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Subject[PATCH][RFC] make cpu_sibling_map a cpumask_t
Hi guys,
This is rather a trivial change but is not for 2.6.0.
The patch is actually on top of some of my HT stuff so one part is
slightly different, but its purpose is to gather feedback.

It turns the cpu_sibling_map array from an array of cpus to an array
of cpumasks. This allows handling of more than 2 siblings, not that
I know of any immediate need.

I think it generalises cpu_sibling_map sufficiently that it can become
generic code. This would allow architecture specific code to build the
sibling map, and then Ingo's or my HT implementations to build their
scheduling descriptions in generic code.

I'm not aware of any reason why the kernel should not become generally
SMT aware. It is sufficiently different to SMP that it is worth
specialising it, although I am only aware of P4 and POWER5 implementations.

Best regards
Nick

P.S.
I have an alternative to Ingo's HT scheduler which basically does
the same thing. It is showing a 20% elapsed time improvement with a
make -j3 on a 2xP4 Xeon (4 logical CPUs).

Before Ingo's is merged, I would like to discuss the pros and cons of
both approaches with those interested. If Ingo's is accepted I should
still be able to port my other SMP/NUMA improvements on top of it.

linux-2.6-npiggin/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c | 9 --
linux-2.6-npiggin/arch/i386/kernel/io_apic.c | 19 ++--
linux-2.6-npiggin/arch/i386/kernel/smpboot.c | 46 +++++------
linux-2.6-npiggin/arch/i386/oprofile/op_model_p4.c | 7 -
linux-2.6-npiggin/include/asm-i386/smp.h | 2
5 files changed, 37 insertions(+), 46 deletions(-)

diff -puN include/asm-i386/smp.h~sibling-map-to-cpumask include/asm-i386/smp.h
--- linux-2.6/include/asm-i386/smp.h~sibling-map-to-cpumask 2003-12-08 14:42:28.000000000 +1100
+++ linux-2.6-npiggin/include/asm-i386/smp.h 2003-12-08 14:42:28.000000000 +1100
@@ -34,7 +34,7 @@
extern void smp_alloc_memory(void);
extern int pic_mode;
extern int smp_num_siblings;
-extern int cpu_sibling_map[];
+extern cpumask_t cpu_sibling_map[];

extern void smp_flush_tlb(void);
extern void smp_message_irq(int cpl, void *dev_id, struct pt_regs *regs);
diff -puN arch/i386/kernel/smpboot.c~sibling-map-to-cpumask arch/i386/kernel/smpboot.c
--- linux-2.6/arch/i386/kernel/smpboot.c~sibling-map-to-cpumask 2003-12-08 14:42:28.000000000 +1100
+++ linux-2.6-npiggin/arch/i386/kernel/smpboot.c 2003-12-08 15:07:48.000000000 +1100
@@ -933,7 +933,7 @@ static int boot_cpu_logical_apicid;
/* Where the IO area was mapped on multiquad, always 0 otherwise */
void *xquad_portio;

-int cpu_sibling_map[NR_CPUS] __cacheline_aligned;
+cpumask_t cpu_sibling_map[NR_CPUS] __cacheline_aligned;

static void __init smp_boot_cpus(unsigned int max_cpus)
{
@@ -1079,32 +1079,28 @@ static void __init smp_boot_cpus(unsigne
Dprintk("Boot done.\n");

/*
- * If Hyper-Threading is avaialble, construct cpu_sibling_map[], so
- * that we can tell the sibling CPU efficiently.
+ * construct cpu_sibling_map[], so that we can tell sibling CPUs
+ * efficiently.
*/
- if (cpu_has_ht && smp_num_siblings > 1) {
- for (cpu = 0; cpu < NR_CPUS; cpu++)
- cpu_sibling_map[cpu] = NO_PROC_ID;
-
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
- int i;
- if (!cpu_isset(cpu, cpu_callout_map))
- continue;
+ for (cpu = 0; cpu < NR_CPUS; cpu++)
+ cpu_sibling_map[cpu] = CPU_MASK_NONE;

- for (i = 0; i < NR_CPUS; i++) {
- if (i == cpu || !cpu_isset(i, cpu_callout_map))
- continue;
- if (phys_proc_id[cpu] == phys_proc_id[i]) {
- cpu_sibling_map[cpu] = i;
- printk("cpu_sibling_map[%d] = %d\n", cpu, cpu_sibling_map[cpu]);
- break;
- }
- }
- if (cpu_sibling_map[cpu] == NO_PROC_ID) {
- smp_num_siblings = 1;
- printk(KERN_WARNING "WARNING: No sibling found for CPU %d.\n", cpu);
+ for (cpu = 0; cpu < NR_CPUS; cpu++) {
+ int siblings = 0;
+ int i;
+ if (!cpu_isset(cpu, cpu_callout_map))
+ continue;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_isset(i, cpu_callout_map))
+ continue;
+ if (phys_proc_id[cpu] == phys_proc_id[i]) {
+ siblings++;
+ cpu_set(i, cpu_sibling_map[cpu]);
}
}
+ if (siblings != smp_num_siblings)
+ printk(KERN_WARNING "WARNING: %d siblings found for CPU%d, should be %d\n", siblings, cpu, smp_num_siblings);
}

smpboot_setup_io_apic();
@@ -1143,8 +1139,8 @@ __init void arch_init_sched_domains(void

*cpu_domain = SD_CPU_INIT;
cpu_domain->span = CPU_MASK_NONE;
- cpu_set(i, cpu_domain->span);
- cpu_set(cpu_sibling_map[i], cpu_domain->span);
+ cpu_domain->span = cpu_sibling_map[i];
+ WARN_ON(!cpu_isset(i, cpu_sibling_map[i]));
cpu_domain->flags |= SD_FLAG_WAKE | SD_FLAG_IDLE;
cpu_domain->cache_hot_time = 0;
cpu_domain->cache_nice_tries = 0;
diff -puN arch/i386/kernel/io_apic.c~sibling-map-to-cpumask arch/i386/kernel/io_apic.c
--- linux-2.6/arch/i386/kernel/io_apic.c~sibling-map-to-cpumask 2003-12-08 14:42:28.000000000 +1100
+++ linux-2.6-npiggin/arch/i386/kernel/io_apic.c 2003-12-08 14:42:28.000000000 +1100
@@ -309,8 +309,7 @@ struct irq_cpu_info {

#define IRQ_ALLOWED(cpu, allowed_mask) cpu_isset(cpu, allowed_mask)

-#define CPU_TO_PACKAGEINDEX(i) \
- ((physical_balance && i > cpu_sibling_map[i]) ? cpu_sibling_map[i] : i)
+#define CPU_TO_PACKAGEINDEX(i) (first_cpu(cpu_sibling_map[i]))

#define MAX_BALANCED_IRQ_INTERVAL (5*HZ)
#define MIN_BALANCED_IRQ_INTERVAL (HZ/2)
@@ -393,6 +392,7 @@ static void do_irq_balance(void)
unsigned long max_cpu_irq = 0, min_cpu_irq = (~0);
unsigned long move_this_load = 0;
int max_loaded = 0, min_loaded = 0;
+ int load;
unsigned long useful_load_threshold = balanced_irq_interval + 10;
int selected_irq;
int tmp_loaded, first_attempt = 1;
@@ -444,7 +444,7 @@ static void do_irq_balance(void)
for (i = 0; i < NR_CPUS; i++) {
if (!cpu_online(i))
continue;
- if (physical_balance && i > cpu_sibling_map[i])
+ if (i != CPU_TO_PACKAGEINDEX(i))
continue;
if (min_cpu_irq > CPU_IRQ(i)) {
min_cpu_irq = CPU_IRQ(i);
@@ -463,7 +463,7 @@ tryanothercpu:
for (i = 0; i < NR_CPUS; i++) {
if (!cpu_online(i))
continue;
- if (physical_balance && i > cpu_sibling_map[i])
+ if (i != CPU_TO_PACKAGEINDEX(i))
continue;
if (max_cpu_irq <= CPU_IRQ(i))
continue;
@@ -543,9 +543,14 @@ tryanotherirq:
* We seek the least loaded sibling by making the comparison
* (A+B)/2 vs B
*/
- if (physical_balance && (CPU_IRQ(min_loaded) >> 1) >
- CPU_IRQ(cpu_sibling_map[min_loaded]))
- min_loaded = cpu_sibling_map[min_loaded];
+ load = CPU_IRQ(min_loaded) >> 1;
+ for_each_cpu(j, cpu_sibling_map[min_loaded]) {
+ if (load > CPU_IRQ(j)) {
+ /* This won't change cpu_sibling_map[min_loaded] */
+ load = CPU_IRQ(j);
+ min_loaded = j;
+ }
+ }

cpus_and(allowed_mask, cpu_online_map, irq_affinity[selected_irq]);
target_cpu_mask = cpumask_of_cpu(min_loaded);
diff -puN arch/i386/kernel/cpu/cpufreq/p4-clockmod.c~sibling-map-to-cpumask arch/i386/kernel/cpu/cpufreq/p4-clockmod.c
--- linux-2.6/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c~sibling-map-to-cpumask 2003-12-08 14:42:28.000000000 +1100
+++ linux-2.6-npiggin/arch/i386/kernel/cpu/cpufreq/p4-clockmod.c 2003-12-08 14:42:28.000000000 +1100
@@ -67,14 +67,7 @@ static int cpufreq_p4_setdc(unsigned int
cpus_allowed = current->cpus_allowed;

/* only run on CPU to be set, or on its sibling */
- affected_cpu_map = cpumask_of_cpu(cpu);
-#ifdef CONFIG_X86_HT
- hyperthreading = ((cpu_has_ht) && (smp_num_siblings == 2));
- if (hyperthreading) {
- sibling = cpu_sibling_map[cpu];
- cpu_set(sibling, affected_cpu_map);
- }
-#endif
+ affected_cpu_map = cpu_sibling_map[cpu];
set_cpus_allowed(current, affected_cpu_map);
BUG_ON(!cpu_isset(smp_processor_id(), affected_cpu_map));

diff -puN arch/i386/oprofile/op_model_p4.c~sibling-map-to-cpumask arch/i386/oprofile/op_model_p4.c
--- linux-2.6/arch/i386/oprofile/op_model_p4.c~sibling-map-to-cpumask 2003-12-08 14:42:28.000000000 +1100
+++ linux-2.6-npiggin/arch/i386/oprofile/op_model_p4.c 2003-12-08 14:42:28.000000000 +1100
@@ -382,11 +382,8 @@ static struct p4_event_binding p4_events
static unsigned int get_stagger(void)
{
#ifdef CONFIG_SMP
- int cpu;
- if (smp_num_siblings > 1) {
- cpu = smp_processor_id();
- return (cpu_sibling_map[cpu] > cpu) ? 0 : 1;
- }
+ int cpu = smp_processor_id();
+ return (cpu != first_cpu(cpu_sibling_map[cpu]));
#endif
return 0;
}
_
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