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Subject[patch] "HT scheduler", sched-2.5.63-B3

this is the latest HT scheduler patch, against 2.5.63-BK. Changes in -B3,
relative to the -A3 patch:

- fix bootup hang caused by an SMP init race. [the race only triggered
when not using serial logging - ugh.]

- fix bootup hang on non-HT SMP boxes compiled with HT-scheduling
support, the active balancer's loop did not handle this case correctly.

- fix over-eager active-balancing due to over-inflated nr_running value
when active-balancing via the migration thread.

This patch has been test-compiled and test-booted it on a HT, SMP and UP
box, everything works.

Ingo

--- linux/include/linux/sched.h.orig
+++ linux/include/linux/sched.h
@@ -147,6 +147,24 @@ typedef struct task_struct task_t;
extern void sched_init(void);
extern void init_idle(task_t *idle, int cpu);

+/*
+ * Is there a way to do this via Kconfig?
+ */
+#if CONFIG_NR_SIBLINGS_2
+# define CONFIG_NR_SIBLINGS 2
+#elif CONFIG_NR_SIBLINGS_4
+# define CONFIG_NR_SIBLINGS 4
+#else
+# define CONFIG_NR_SIBLINGS 0
+#endif
+
+#if CONFIG_NR_SIBLINGS
+# define CONFIG_SHARE_RUNQUEUE 1
+#else
+# define CONFIG_SHARE_RUNQUEUE 0
+#endif
+extern void sched_map_runqueue(int cpu1, int cpu2);
+
extern void show_state(void);
extern void show_trace(unsigned long *stack);
extern void show_stack(unsigned long *stack);
@@ -328,7 +346,7 @@ struct task_struct {
prio_array_t *array;

unsigned long sleep_avg;
- unsigned long sleep_timestamp;
+ unsigned long last_run;

unsigned long policy;
unsigned long cpus_allowed;
@@ -803,11 +821,6 @@ static inline unsigned int task_cpu(stru
return p->thread_info->cpu;
}

-static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
-{
- p->thread_info->cpu = cpu;
-}
-
#else

static inline unsigned int task_cpu(struct task_struct *p)
@@ -815,10 +828,6 @@ static inline unsigned int task_cpu(stru
return 0;
}

-static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
-{
-}
-
#endif /* CONFIG_SMP */

#endif /* __KERNEL__ */
--- linux/include/asm-i386/apic.h.orig
+++ linux/include/asm-i386/apic.h
@@ -98,4 +98,6 @@ extern unsigned int nmi_watchdog;

#endif /* CONFIG_X86_LOCAL_APIC */

+extern int phys_proc_id[NR_CPUS];
+
#endif /* __ASM_APIC_H */
--- linux/arch/i386/kernel/cpu/proc.c.orig
+++ linux/arch/i386/kernel/cpu/proc.c
@@ -1,4 +1,5 @@
#include <linux/smp.h>
+#include <linux/sched.h>
#include <linux/timex.h>
#include <linux/string.h>
#include <asm/semaphore.h>
@@ -101,6 +102,13 @@ static int show_cpuinfo(struct seq_file
fpu_exception ? "yes" : "no",
c->cpuid_level,
c->wp_works_ok ? "yes" : "no");
+#if CONFIG_SHARE_RUNQUEUE
+{
+ extern long __rq_idx[NR_CPUS];
+
+ seq_printf(m, "\nrunqueue\t: %ld\n", __rq_idx[n]);
+}
+#endif

for ( i = 0 ; i < 32*NCAPINTS ; i++ )
if ( test_bit(i, c->x86_capability) &&
--- linux/arch/i386/kernel/smpboot.c.orig
+++ linux/arch/i386/kernel/smpboot.c
@@ -38,6 +38,7 @@
#include <linux/kernel.h>

#include <linux/mm.h>
+#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/smp_lock.h>
#include <linux/irq.h>
@@ -939,6 +940,16 @@ void *xquad_portio;

int cpu_sibling_map[NR_CPUS] __cacheline_aligned;

+static int test_ht;
+
+static int __init ht_setup(char *str)
+{
+ test_ht = 1;
+ return 1;
+}
+
+__setup("test_ht", ht_setup);
+
static void __init smp_boot_cpus(unsigned int max_cpus)
{
int apicid, cpu, bit;
@@ -1079,7 +1090,20 @@ static void __init smp_boot_cpus(unsigne
Dprintk("Boot done.\n");

/*
- * If Hyper-Threading is avaialble, construct cpu_sibling_map[], so
+ * Here we can be sure that there is an IO-APIC in the system. Let's
+ * go and set it up:
+ */
+ smpboot_setup_io_apic();
+
+ setup_boot_APIC_clock();
+
+ /*
+ * Synchronize the TSC with the AP
+ */
+ if (cpu_has_tsc && cpucount)
+ synchronize_tsc_bp();
+ /*
+ * If Hyper-Threading is available, construct cpu_sibling_map[], so
* that we can tell the sibling CPU efficiently.
*/
if (cpu_has_ht && smp_num_siblings > 1) {
@@ -1088,7 +1112,8 @@ static void __init smp_boot_cpus(unsigne

for (cpu = 0; cpu < NR_CPUS; cpu++) {
int i;
- if (!test_bit(cpu, &cpu_callout_map)) continue;
+ if (!test_bit(cpu, &cpu_callout_map))
+ continue;

for (i = 0; i < NR_CPUS; i++) {
if (i == cpu || !test_bit(i, &cpu_callout_map))
@@ -1104,17 +1129,41 @@ static void __init smp_boot_cpus(unsigne
printk(KERN_WARNING "WARNING: No sibling found for CPU %d.\n", cpu);
}
}
- }
-
- smpboot_setup_io_apic();
-
- setup_boot_APIC_clock();
+#if CONFIG_SHARE_RUNQUEUE
+ /*
+ * At this point APs would have synchronised TSC and
+ * waiting for smp_commenced, with their APIC timer
+ * disabled. So BP can go ahead do some initialization
+ * for Hyper-Threading (if needed).
+ */
+ for (cpu = 0; cpu < NR_CPUS; cpu++) {
+ int i;
+ if (!test_bit(cpu, &cpu_callout_map))
+ continue;
+ for (i = 0; i < NR_CPUS; i++) {
+ if (i <= cpu)
+ continue;
+ if (!test_bit(i, &cpu_callout_map))
+ continue;

- /*
- * Synchronize the TSC with the AP
- */
- if (cpu_has_tsc && cpucount)
- synchronize_tsc_bp();
+ if (phys_proc_id[cpu] != phys_proc_id[i])
+ continue;
+ /*
+ * merge runqueues, resulting in one
+ * runqueue per package:
+ */
+ sched_map_runqueue(cpu, i);
+ break;
+ }
+ }
+#endif
+ }
+#if CONFIG_SHARE_RUNQUEUE
+ if (smp_num_siblings == 1 && test_ht) {
+ printk("Simulating shared runqueues - mapping CPU#1's runqueue to CPU#0's runqueue.\n");
+ sched_map_runqueue(0, 1);
+ }
+#endif
}

/* These are wrappers to interface to the new boot process. Someone
--- linux/arch/i386/Kconfig.orig
+++ linux/arch/i386/Kconfig
@@ -422,6 +422,24 @@ config SMP

If you don't know what to do here, say N.

+choice
+
+ prompt "Hyperthreading Support"
+ depends on SMP
+ default NR_SIBLINGS_0
+
+config NR_SIBLINGS_0
+ bool "off"
+
+config NR_SIBLINGS_2
+ bool "2 siblings"
+
+config NR_SIBLINGS_4
+ bool "4 siblings"
+
+endchoice
+
+
config PREEMPT
bool "Preemptible Kernel"
help
--- linux/kernel/fork.c.orig
+++ linux/kernel/fork.c
@@ -916,7 +916,7 @@ static struct task_struct *copy_process(
*/
p->first_time_slice = 1;
current->time_slice >>= 1;
- p->sleep_timestamp = jiffies;
+ p->last_run = jiffies;
if (!current->time_slice) {
/*
* This case is rare, it happens when the parent has only
--- linux/kernel/sched.c.orig
+++ linux/kernel/sched.c
@@ -67,6 +67,7 @@
#define INTERACTIVE_DELTA 2
#define MAX_SLEEP_AVG (2*HZ)
#define STARVATION_LIMIT (2*HZ)
+#define AGRESSIVE_IDLE_STEAL 1
#define NODE_THRESHOLD 125

/*
@@ -141,6 +142,48 @@ struct prio_array {
};

/*
+ * It's possible for two CPUs to share the same runqueue.
+ * This makes sense if they eg. share caches.
+ *
+ * We take the common 1:1 (SMP, UP) case and optimize it,
+ * the rest goes via remapping: rq_idx(cpu) gives the
+ * runqueue on which a particular cpu is on, cpu_idx(cpu)
+ * gives the rq-specific index of the cpu.
+ *
+ * (Note that the generic scheduler code does not impose any
+ * restrictions on the mappings - there can be 4 CPUs per
+ * runqueue or even assymetric mappings.)
+ */
+#if CONFIG_SHARE_RUNQUEUE
+# define MAX_NR_SIBLINGS CONFIG_NR_SIBLINGS
+ long __rq_idx[NR_CPUS] __cacheline_aligned;
+ static long __cpu_idx[NR_CPUS] __cacheline_aligned;
+# define rq_idx(cpu) (__rq_idx[(cpu)])
+# define cpu_idx(cpu) (__cpu_idx[(cpu)])
+# define for_each_sibling(idx, rq) \
+ for ((idx) = 0; (idx) < (rq)->nr_cpus; (idx)++)
+# define rq_nr_cpus(rq) ((rq)->nr_cpus)
+# define cpu_active_balance(c) (cpu_rq(c)->cpu[0].active_balance)
+#else
+# define MAX_NR_SIBLINGS 1
+# define rq_idx(cpu) (cpu)
+# define cpu_idx(cpu) 0
+# define for_each_sibling(idx, rq) while (0)
+# define cpu_active_balance(c) 0
+# define do_active_balance(rq, cpu) do { } while (0)
+# define rq_nr_cpus(rq) 1
+ static inline void active_load_balance(runqueue_t *rq, int this_cpu) { }
+#endif
+
+typedef struct cpu_s {
+ task_t *curr, *idle;
+ task_t *migration_thread;
+ struct list_head migration_queue;
+ int active_balance;
+ int cpu;
+} cpu_t;
+
+/*
* This is the main, per-CPU runqueue data structure.
*
* Locking rule: those places that want to lock multiple runqueues
@@ -151,7 +194,6 @@ struct runqueue {
spinlock_t lock;
unsigned long nr_running, nr_switches, expired_timestamp,
nr_uninterruptible;
- task_t *curr, *idle;
struct mm_struct *prev_mm;
prio_array_t *active, *expired, arrays[2];
int prev_nr_running[NR_CPUS];
@@ -160,27 +202,39 @@ struct runqueue {
unsigned int nr_balanced;
int prev_node_load[MAX_NUMNODES];
#endif
- task_t *migration_thread;
- struct list_head migration_queue;
+ int nr_cpus;
+ cpu_t cpu[MAX_NR_SIBLINGS];

atomic_t nr_iowait;
} ____cacheline_aligned;

static struct runqueue runqueues[NR_CPUS] __cacheline_aligned;

-#define cpu_rq(cpu) (runqueues + (cpu))
+#define cpu_rq(cpu) (runqueues + (rq_idx(cpu)))
+#define cpu_int(c) ((cpu_rq(c))->cpu + cpu_idx(c))
+#define cpu_curr_ptr(cpu) (cpu_int(cpu)->curr)
+#define cpu_idle_ptr(cpu) (cpu_int(cpu)->idle)
+
#define this_rq() cpu_rq(smp_processor_id())
#define task_rq(p) cpu_rq(task_cpu(p))
-#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
#define rt_task(p) ((p)->prio < MAX_RT_PRIO)

+#define migration_thread(cpu) (cpu_int(cpu)->migration_thread)
+#define migration_queue(cpu) (&cpu_int(cpu)->migration_queue)
+
+#if NR_CPUS > 1
+# define task_allowed(p, cpu) ((p)->cpus_allowed & (1UL << (cpu)))
+#else
+# define task_allowed(p, cpu) 1
+#endif
+
/*
* Default context-switch locking:
*/
#ifndef prepare_arch_switch
# define prepare_arch_switch(rq, next) do { } while(0)
# define finish_arch_switch(rq, next) spin_unlock_irq(&(rq)->lock)
-# define task_running(rq, p) ((rq)->curr == (p))
+# define task_running(p) (cpu_curr_ptr(task_cpu(p)) == (p))
#endif

#ifdef CONFIG_NUMA
@@ -323,16 +377,21 @@ static inline int effective_prio(task_t
* Also update all the scheduling statistics stuff. (sleep average
* calculation, priority modifiers, etc.)
*/
+static inline void __activate_task(task_t *p, runqueue_t *rq)
+{
+ enqueue_task(p, rq->active);
+ nr_running_inc(rq);
+}
+
static inline void activate_task(task_t *p, runqueue_t *rq)
{
- unsigned long sleep_time = jiffies - p->sleep_timestamp;
- prio_array_t *array = rq->active;
+ unsigned long sleep_time = jiffies - p->last_run;

if (!rt_task(p) && sleep_time) {
/*
* This code gives a bonus to interactive tasks. We update
* an 'average sleep time' value here, based on
- * sleep_timestamp. The more time a task spends sleeping,
+ * ->last_run. The more time a task spends sleeping,
* the higher the average gets - and the higher the priority
* boost gets as well.
*/
@@ -341,8 +400,7 @@ static inline void activate_task(task_t
p->sleep_avg = MAX_SLEEP_AVG;
p->prio = effective_prio(p);
}
- enqueue_task(p, array);
- nr_running_inc(rq);
+ __activate_task(p, rq);
}

/*
@@ -383,8 +441,18 @@ static inline void resched_task(task_t *
#endif
}

+static inline void resched_cpu(int cpu)
+{
+ resched_task(cpu_curr_ptr(cpu));
+}
+
#ifdef CONFIG_SMP

+static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
+{
+ p->thread_info->cpu = cpu;
+}
+
/*
* wait_task_inactive - wait for a thread to unschedule.
*
@@ -402,7 +470,7 @@ void wait_task_inactive(task_t * p)
repeat:
preempt_disable();
rq = task_rq(p);
- if (unlikely(task_running(rq, p))) {
+ if (unlikely(task_running(p))) {
cpu_relax();
/*
* enable/disable preemption just to make this
@@ -413,7 +481,7 @@ repeat:
goto repeat;
}
rq = task_rq_lock(p, &flags);
- if (unlikely(task_running(rq, p))) {
+ if (unlikely(task_running(p))) {
task_rq_unlock(rq, &flags);
preempt_enable();
goto repeat;
@@ -421,6 +489,13 @@ repeat:
task_rq_unlock(rq, &flags);
preempt_enable();
}
+
+#else
+
+static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
+{
+}
+
#endif

/*
@@ -435,10 +510,39 @@ repeat:
*/
void kick_if_running(task_t * p)
{
- if ((task_running(task_rq(p), p)) && (task_cpu(p) != smp_processor_id()))
+ if ((task_running(p)) && (task_cpu(p) != smp_processor_id()))
resched_task(p);
}

+static void wake_up_cpu(runqueue_t *rq, int cpu, task_t *p)
+{
+ cpu_t *curr_cpu;
+ task_t *curr;
+ int idx;
+
+ if (idle_cpu(cpu))
+ return resched_cpu(cpu);
+
+ for_each_sibling(idx, rq) {
+ curr_cpu = rq->cpu + idx;
+ if (!task_allowed(p, curr_cpu->cpu))
+ continue;
+ if (curr_cpu->idle == curr_cpu->curr)
+ return resched_cpu(curr_cpu->cpu);
+ }
+
+ if (p->prio < cpu_curr_ptr(cpu)->prio)
+ return resched_task(cpu_curr_ptr(cpu));
+
+ for_each_sibling(idx, rq) {
+ curr_cpu = rq->cpu + idx;
+ if (!task_allowed(p, curr_cpu->cpu))
+ continue;
+ curr = curr_cpu->curr;
+ if (p->prio < curr->prio)
+ return resched_task(curr);
+ }
+}
/***
* try_to_wake_up - wake up a thread
* @p: the to-be-woken-up thread
@@ -460,6 +564,7 @@ static int try_to_wake_up(task_t * p, un
long old_state;
runqueue_t *rq;

+ BUG_ON(!p);
repeat_lock_task:
rq = task_rq_lock(p, &flags);
old_state = p->state;
@@ -469,7 +574,7 @@ repeat_lock_task:
* Fast-migrate the task if it's not running or runnable
* currently. Do not violate hard affinity.
*/
- if (unlikely(sync && !task_running(rq, p) &&
+ if (unlikely(sync && !task_running(p) &&
(task_cpu(p) != smp_processor_id()) &&
(p->cpus_allowed & (1UL << smp_processor_id())))) {

@@ -479,10 +584,12 @@ repeat_lock_task:
}
if (old_state == TASK_UNINTERRUPTIBLE)
rq->nr_uninterruptible--;
- activate_task(p, rq);
-
- if (p->prio < rq->curr->prio)
- resched_task(rq->curr);
+ if (sync)
+ __activate_task(p, rq);
+ else {
+ activate_task(p, rq);
+ wake_up_cpu(rq, task_cpu(p), p);
+ }
success = 1;
}
p->state = TASK_RUNNING;
@@ -605,7 +712,7 @@ static inline task_t * context_switch(ru
{
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
-
+
if (unlikely(!mm)) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
@@ -637,8 +744,9 @@ unsigned long nr_running(void)
unsigned long i, sum = 0;

for (i = 0; i < NR_CPUS; i++)
- sum += cpu_rq(i)->nr_running;
-
+ /* Shared runqueues are counted only once. */
+ if (!cpu_idx(i))
+ sum += cpu_rq(i)->nr_running;
return sum;
}

@@ -649,7 +757,9 @@ unsigned long nr_uninterruptible(void)
for (i = 0; i < NR_CPUS; i++) {
if (!cpu_online(i))
continue;
- sum += cpu_rq(i)->nr_uninterruptible;
+ /* Shared runqueues are counted only once. */
+ if (!cpu_idx(i))
+ sum += cpu_rq(i)->nr_uninterruptible;
}
return sum;
}
@@ -831,7 +941,23 @@ static inline unsigned long cpus_to_bala

#endif /* CONFIG_NUMA */

-#if CONFIG_SMP
+/*
+ * One of the idle_cpu_tick() and busy_cpu_tick() functions will
+ * get called every timer tick, on every CPU. Our balancing action
+ * frequency and balancing agressivity depends on whether the CPU is
+ * idle or not.
+ *
+ * busy-rebalance every 250 msecs. idle-rebalance every 1 msec. (or on
+ * systems with HZ=100, every 10 msecs.)
+ */
+#define BUSY_REBALANCE_TICK (HZ/4 ?: 1)
+#define IDLE_REBALANCE_TICK (HZ/1000 ?: 1)
+
+#if !CONFIG_SMP
+
+static inline void load_balance(runqueue_t *rq, int this_cpu, int idle) { }
+
+#else

/*
* double_lock_balance - lock the busiest runqueue
@@ -947,12 +1073,7 @@ static inline void pull_task(runqueue_t
set_task_cpu(p, this_cpu);
nr_running_inc(this_rq);
enqueue_task(p, this_rq->active);
- /*
- * Note that idle threads have a prio of MAX_PRIO, for this test
- * to be always true for them.
- */
- if (p->prio < this_rq->curr->prio)
- set_need_resched();
+ wake_up_cpu(this_rq, this_cpu, p);
}

/*
@@ -963,9 +1084,9 @@ static inline void pull_task(runqueue_t
* We call this with the current runqueue locked,
* irqs disabled.
*/
-static void load_balance(runqueue_t *this_rq, int idle)
+static void load_balance(runqueue_t *this_rq, int this_cpu, int idle)
{
- int imbalance, idx, this_cpu = smp_processor_id();
+ int imbalance, idx;
runqueue_t *busiest;
prio_array_t *array;
struct list_head *head, *curr;
@@ -1013,12 +1134,15 @@ skip_queue:
* 1) running (obviously), or
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
+ *
+ * (except if we are in idle mode which is a more agressive
+ * form of rebalancing.)
*/

-#define CAN_MIGRATE_TASK(p,rq,this_cpu) \
- ((jiffies - (p)->sleep_timestamp > cache_decay_ticks) && \
- !task_running(rq, p) && \
- ((p)->cpus_allowed & (1UL << (this_cpu))))
+#define CAN_MIGRATE_TASK(p,rq,cpu) \
+ (((idle && AGRESSIVE_IDLE_STEAL) || \
+ (jiffies - (p)->last_run > cache_decay_ticks)) && \
+ !task_running(p) && task_allowed(p, cpu))

curr = curr->prev;

@@ -1041,31 +1165,144 @@ out:
;
}

+#if CONFIG_SHARE_RUNQUEUE
+static void active_load_balance(runqueue_t *this_rq, int this_cpu)
+{
+ runqueue_t *rq;
+ int i, idx;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_online(i))
+ continue;
+ rq = cpu_rq(i);
+ if (rq == this_rq)
+ continue;
+ /*
+ * If there's only one CPU mapped to this runqueue
+ * then there can be no SMT imbalance:
+ */
+ if (rq->nr_cpus == 1)
+ continue;
+ /*
+ * Any SMT-specific imbalance?
+ */
+ for_each_sibling(idx, rq)
+ if (rq->cpu[idx].idle == rq->cpu[idx].curr)
+ continue;
+
+ /*
+ * At this point it's sure that we have a SMT
+ * imbalance: this (physical) CPU is idle but
+ * another CPU has two (or more) tasks running.
+ *
+ * We wake up one of the migration threads (it
+ * doesnt matter which one) and let it fix things up:
+ */
+ if (!cpu_active_balance(i)) {
+ cpu_active_balance(i) = 1;
+ spin_unlock(&this_rq->lock);
+ if (rq->cpu[0].migration_thread)
+ wake_up_process(rq->cpu[0].migration_thread);
+ spin_lock(&this_rq->lock);
+ }
+ }
+}
+
+static void do_active_balance(runqueue_t *this_rq, int this_cpu)
+{
+ runqueue_t *rq;
+ int i, idx;
+
+ spin_unlock(&this_rq->lock);
+
+ cpu_active_balance(this_cpu) = 0;
+
+ /*
+ * Is the imbalance still present?
+ */
+ for_each_sibling(idx, this_rq)
+ if (this_rq->cpu[idx].idle == this_rq->cpu[idx].curr)
+ goto out;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_online(i))
+ continue;
+ rq = cpu_rq(i);
+ if (rq == this_rq)
+ continue;
+
+ /* completely idle CPU? */
+ if (rq->nr_running)
+ continue;
+
+ /*
+ * At this point it's reasonably sure that we have an
+ * imbalance. Since we are the migration thread, try to
+ * balance a thread over to the target queue.
+ */
+ spin_lock(&this_rq->lock);
+ this_rq->nr_running--;
+ spin_unlock(&this_rq->lock);
+
+ spin_lock(&rq->lock);
+ load_balance(rq, i, 1);
+ spin_unlock(&rq->lock);
+
+ spin_lock(&this_rq->lock);
+ this_rq->nr_running++;
+ spin_unlock(&this_rq->lock);
+ goto out;
+ }
+out:
+ spin_lock(&this_rq->lock);
+}
+
/*
- * One of the idle_cpu_tick() and busy_cpu_tick() functions will
- * get called every timer tick, on every CPU. Our balancing action
- * frequency and balancing agressivity depends on whether the CPU is
- * idle or not.
+ * This routine is called to map a CPU into another CPU's runqueue.
*
- * busy-rebalance every 250 msecs. idle-rebalance every 1 msec. (or on
- * systems with HZ=100, every 10 msecs.)
+ * This must be called during bootup with the merged runqueue having
+ * no tasks.
*/
-#define BUSY_REBALANCE_TICK (HZ/4 ?: 1)
-#define IDLE_REBALANCE_TICK (HZ/1000 ?: 1)
+void sched_map_runqueue(int cpu1, int cpu2)
+{
+ runqueue_t *rq1 = cpu_rq(cpu1);
+ runqueue_t *rq2 = cpu_rq(cpu2);
+ int cpu2_idx_orig = cpu_idx(cpu2), cpu2_idx;
+
+ BUG_ON(rq1 == rq2 || rq2->nr_running || rq_idx(cpu1) != cpu1);
+ /*
+ * At this point, we dont have anything in the runqueue yet. So,
+ * there is no need to move processes between the runqueues.
+ * Only, the idle processes should be combined and accessed
+ * properly.
+ */
+ cpu2_idx = rq1->nr_cpus++;
+
+ rq_idx(cpu2) = cpu1;
+ cpu_idx(cpu2) = cpu2_idx;
+ rq1->cpu[cpu2_idx].cpu = cpu2;
+ rq1->cpu[cpu2_idx].idle = rq2->cpu[cpu2_idx_orig].idle;
+ rq1->cpu[cpu2_idx].curr = rq2->cpu[cpu2_idx_orig].curr;
+ INIT_LIST_HEAD(&rq1->cpu[cpu2_idx].migration_queue);

-static inline void idle_tick(runqueue_t *rq)
+ /* just to be safe: */
+ rq2->cpu[cpu2_idx_orig].idle = NULL;
+ rq2->cpu[cpu2_idx_orig].curr = NULL;
+}
+#endif
+#endif
+
+DEFINE_PER_CPU(struct kernel_stat, kstat) = { { 0 } };
+
+static inline void idle_tick(runqueue_t *rq, unsigned long j)
{
- if (jiffies % IDLE_REBALANCE_TICK)
+ if (j % IDLE_REBALANCE_TICK)
return;
spin_lock(&rq->lock);
- load_balance(rq, 1);
+ load_balance(rq, smp_processor_id(), 1);
spin_unlock(&rq->lock);
}

-#endif
-
-DEFINE_PER_CPU(struct kernel_stat, kstat) = { { 0 } };
-
/*
* We place interactive tasks back into the active array, if possible.
*
@@ -1076,9 +1313,9 @@ DEFINE_PER_CPU(struct kernel_stat, kstat
* increasing number of running tasks:
*/
#define EXPIRED_STARVING(rq) \
- ((rq)->expired_timestamp && \
+ (STARVATION_LIMIT && ((rq)->expired_timestamp && \
(jiffies - (rq)->expired_timestamp >= \
- STARVATION_LIMIT * ((rq)->nr_running) + 1))
+ STARVATION_LIMIT * ((rq)->nr_running) + 1)))

/*
* This function gets called by the timer code, with HZ frequency.
@@ -1091,12 +1328,13 @@ void scheduler_tick(int user_ticks, int
{
int cpu = smp_processor_id();
runqueue_t *rq = this_rq();
+ unsigned long j = jiffies;
task_t *p = current;

if (rcu_pending(cpu))
rcu_check_callbacks(cpu, user_ticks);

- if (p == rq->idle) {
+ if (p == cpu_idle_ptr(cpu)) {
/* note: this timer irq context must be accounted for as well */
if (irq_count() - HARDIRQ_OFFSET >= SOFTIRQ_OFFSET)
kstat_cpu(cpu).cpustat.system += sys_ticks;
@@ -1104,9 +1342,7 @@ void scheduler_tick(int user_ticks, int
kstat_cpu(cpu).cpustat.iowait += sys_ticks;
else
kstat_cpu(cpu).cpustat.idle += sys_ticks;
-#if CONFIG_SMP
- idle_tick(rq);
-#endif
+ idle_tick(rq, j);
return;
}
if (TASK_NICE(p) > 0)
@@ -1115,12 +1351,13 @@ void scheduler_tick(int user_ticks, int
kstat_cpu(cpu).cpustat.user += user_ticks;
kstat_cpu(cpu).cpustat.system += sys_ticks;

+ spin_lock(&rq->lock);
/* Task might have expired already, but not scheduled off yet */
if (p->array != rq->active) {
set_tsk_need_resched(p);
+ spin_unlock(&rq->lock);
return;
}
- spin_lock(&rq->lock);
if (unlikely(rt_task(p))) {
/*
* RR tasks need a special form of timeslice management.
@@ -1156,16 +1393,14 @@ void scheduler_tick(int user_ticks, int

if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
if (!rq->expired_timestamp)
- rq->expired_timestamp = jiffies;
+ rq->expired_timestamp = j;
enqueue_task(p, rq->expired);
} else
enqueue_task(p, rq->active);
}
out:
-#if CONFIG_SMP
- if (!(jiffies % BUSY_REBALANCE_TICK))
- load_balance(rq, 0);
-#endif
+ if (!(j % BUSY_REBALANCE_TICK))
+ load_balance(rq, smp_processor_id(), 0);
spin_unlock(&rq->lock);
}

@@ -1176,11 +1411,11 @@ void scheduling_functions_start_here(voi
*/
asmlinkage void schedule(void)
{
+ int idx, this_cpu, retry = 0;
+ struct list_head *queue;
task_t *prev, *next;
- runqueue_t *rq;
prio_array_t *array;
- struct list_head *queue;
- int idx;
+ runqueue_t *rq;

/*
* Test if we are atomic. Since do_exit() needs to call into
@@ -1193,15 +1428,15 @@ asmlinkage void schedule(void)
dump_stack();
}
}
-
- check_highmem_ptes();
need_resched:
+ check_highmem_ptes();
+ this_cpu = smp_processor_id();
preempt_disable();
prev = current;
rq = this_rq();

release_kernel_lock(prev);
- prev->sleep_timestamp = jiffies;
+ prev->last_run = jiffies;
spin_lock_irq(&rq->lock);

/*
@@ -1224,12 +1459,14 @@ need_resched:
}
pick_next_task:
if (unlikely(!rq->nr_running)) {
-#if CONFIG_SMP
- load_balance(rq, 1);
+ load_balance(rq, this_cpu, 1);
if (rq->nr_running)
goto pick_next_task;
-#endif
- next = rq->idle;
+ active_load_balance(rq, this_cpu);
+ if (rq->nr_running)
+ goto pick_next_task;
+pick_idle:
+ next = cpu_idle_ptr(this_cpu);
rq->expired_timestamp = 0;
goto switch_tasks;
}
@@ -1245,18 +1482,49 @@ pick_next_task:
rq->expired_timestamp = 0;
}

+new_array:
idx = sched_find_first_bit(array->bitmap);
queue = array->queue + idx;
next = list_entry(queue->next, task_t, run_list);
+ if ((next != prev) && (rq_nr_cpus(rq) > 1)) {
+ struct list_head *tmp = queue->next;
+
+ while ((task_running(next) && (next != prev)) || !task_allowed(next, this_cpu)) {
+ tmp = tmp->next;
+ if (tmp != queue) {
+ next = list_entry(tmp, task_t, run_list);
+ continue;
+ }
+ idx = find_next_bit(array->bitmap, MAX_PRIO, ++idx);
+ if (idx == MAX_PRIO) {
+ if (retry || !rq->expired->nr_active) {
+ goto pick_idle;
+ }
+ /*
+ * To avoid infinite changing of arrays,
+ * when we have only tasks runnable by
+ * sibling.
+ */
+ retry = 1;
+
+ array = rq->expired;
+ goto new_array;
+ }
+ queue = array->queue + idx;
+ tmp = queue->next;
+ next = list_entry(tmp, task_t, run_list);
+ }
+ }

switch_tasks:
prefetch(next);
clear_tsk_need_resched(prev);
- RCU_qsctr(prev->thread_info->cpu)++;
+ RCU_qsctr(task_cpu(prev))++;

if (likely(prev != next)) {
rq->nr_switches++;
- rq->curr = next;
+ cpu_curr_ptr(this_cpu) = next;
+ set_task_cpu(next, this_cpu);

prepare_arch_switch(rq, next);
prev = context_switch(rq, prev, next);
@@ -1522,9 +1790,8 @@ void set_user_nice(task_t *p, long nice)
* If the task is running and lowered its priority,
* or increased its priority then reschedule its CPU:
*/
- if ((NICE_TO_PRIO(nice) < p->static_prio) ||
- task_running(rq, p))
- resched_task(rq->curr);
+ if ((NICE_TO_PRIO(nice) < p->static_prio) || task_running(p))
+ resched_task(cpu_curr_ptr(task_cpu(p)));
}
out_unlock:
task_rq_unlock(rq, &flags);
@@ -1602,7 +1869,7 @@ int task_nice(task_t *p)
*/
int task_curr(task_t *p)
{
- return cpu_curr(task_cpu(p)) == p;
+ return cpu_curr_ptr(task_cpu(p)) == p;
}

/**
@@ -1611,7 +1878,7 @@ int task_curr(task_t *p)
*/
int idle_cpu(int cpu)
{
- return cpu_curr(cpu) == cpu_rq(cpu)->idle;
+ return cpu_curr_ptr(cpu) == cpu_idle_ptr(cpu);
}

/**
@@ -1701,7 +1968,7 @@ static int setscheduler(pid_t pid, int p
else
p->prio = p->static_prio;
if (array)
- activate_task(p, task_rq(p));
+ __activate_task(p, task_rq(p));

out_unlock:
task_rq_unlock(rq, &flags);
@@ -2161,7 +2428,7 @@ void __init init_idle(task_t *idle, int
local_irq_save(flags);
double_rq_lock(idle_rq, rq);

- idle_rq->curr = idle_rq->idle = idle;
+ cpu_curr_ptr(cpu) = cpu_idle_ptr(cpu) = idle;
deactivate_task(idle, rq);
idle->array = NULL;
idle->prio = MAX_PRIO;
@@ -2216,6 +2483,7 @@ void set_cpus_allowed(task_t *p, unsigne
unsigned long flags;
migration_req_t req;
runqueue_t *rq;
+ int cpu;

#if 0 /* FIXME: Grab cpu_lock, return error on this case. --RR */
new_mask &= cpu_online_map;
@@ -2237,31 +2505,31 @@ void set_cpus_allowed(task_t *p, unsigne
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
- if (!p->array && !task_running(rq, p)) {
+ if (!p->array && !task_running(p)) {
set_task_cpu(p, __ffs(p->cpus_allowed));
task_rq_unlock(rq, &flags);
return;
}
init_completion(&req.done);
req.task = p;
- list_add(&req.list, &rq->migration_queue);
+ cpu = task_cpu(p);
+ list_add(&req.list, migration_queue(cpu));
task_rq_unlock(rq, &flags);
-
- wake_up_process(rq->migration_thread);
+ wake_up_process(migration_thread(cpu));

wait_for_completion(&req.done);
}

/*
- * migration_thread - this is a highprio system thread that performs
+ * migration_task - this is a highprio system thread that performs
* thread migration by 'pulling' threads into the target runqueue.
*/
-static int migration_thread(void * data)
+static int migration_task(void * data)
{
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
int cpu = (long) data;
runqueue_t *rq;
- int ret;
+ int ret, idx;

daemonize("migration/%d", cpu);
set_fs(KERNEL_DS);
@@ -2275,7 +2543,8 @@ static int migration_thread(void * data)
ret = setscheduler(0, SCHED_FIFO, &param);

rq = this_rq();
- rq->migration_thread = current;
+ migration_thread(cpu) = current;
+ idx = cpu_idx(cpu);

for (;;) {
runqueue_t *rq_src, *rq_dest;
@@ -2286,8 +2555,10 @@ static int migration_thread(void * data)
task_t *p;

spin_lock_irqsave(&rq->lock, flags);
- head = &rq->migration_queue;
- current->state = TASK_INTERRUPTIBLE;
+ if (cpu_active_balance(cpu))
+ do_active_balance(rq, cpu);
+ head = migration_queue(cpu);
+ current->state = TASK_UNINTERRUPTIBLE;
if (list_empty(head)) {
spin_unlock_irqrestore(&rq->lock, flags);
schedule();
@@ -2315,9 +2586,8 @@ repeat:
set_task_cpu(p, cpu_dest);
if (p->array) {
deactivate_task(p, rq_src);
- activate_task(p, rq_dest);
- if (p->prio < rq_dest->curr->prio)
- resched_task(rq_dest->curr);
+ __activate_task(p, rq_dest);
+ wake_up_cpu(rq_dest, cpu_dest, p);
}
}
double_rq_unlock(rq_src, rq_dest);
@@ -2335,12 +2605,13 @@ static int migration_call(struct notifie
unsigned long action,
void *hcpu)
{
+ long cpu = (long) hcpu;
+
switch (action) {
case CPU_ONLINE:
- printk("Starting migration thread for cpu %li\n",
- (long)hcpu);
- kernel_thread(migration_thread, hcpu, CLONE_KERNEL);
- while (!cpu_rq((long)hcpu)->migration_thread)
+ printk("Starting migration thread for cpu %li\n", cpu);
+ kernel_thread(migration_task, hcpu, CLONE_KERNEL);
+ while (!migration_thread(cpu))
yield();
break;
}
@@ -2415,11 +2686,20 @@ void __init sched_init(void)
for (i = 0; i < NR_CPUS; i++) {
prio_array_t *array;

+ /*
+ * Start with a 1:1 mapping between CPUs and runqueues:
+ */
+#if CONFIG_SHARE_RUNQUEUE
+ rq_idx(i) = i;
+ cpu_idx(i) = 0;
+#endif
rq = cpu_rq(i);
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
spin_lock_init(&rq->lock);
- INIT_LIST_HEAD(&rq->migration_queue);
+ INIT_LIST_HEAD(migration_queue(i));
+ rq->nr_cpus = 1;
+ rq->cpu[cpu_idx(i)].cpu = i;
atomic_set(&rq->nr_iowait, 0);
nr_running_init(rq);

@@ -2437,9 +2717,9 @@ void __init sched_init(void)
* We have to do a little magic to get the first
* thread right in SMP mode.
*/
- rq = this_rq();
- rq->curr = current;
- rq->idle = current;
+ cpu_curr_ptr(smp_processor_id()) = current;
+ cpu_idle_ptr(smp_processor_id()) = current;
+
set_task_cpu(current, smp_processor_id());
wake_up_forked_process(current);

--- linux/init/main.c.orig
+++ linux/init/main.c
@@ -354,7 +354,14 @@ static void __init smp_init(void)

static void rest_init(void)
{
+ /*
+ * We count on the initial thread going ok
+ * Like idlers init is an unlocked kernel thread, which will
+ * make syscalls (and thus be locked).
+ */
+ init_idle(current, smp_processor_id());
kernel_thread(init, NULL, CLONE_KERNEL);
+
unlock_kernel();
cpu_idle();
}
@@ -438,13 +445,6 @@ asmlinkage void __init start_kernel(void
check_bugs();
printk("POSIX conformance testing by UNIFIX\n");

- /*
- * We count on the initial thread going ok
- * Like idlers init is an unlocked kernel thread, which will
- * make syscalls (and thus be locked).
- */
- init_idle(current, smp_processor_id());
-
/* Do the rest non-__init'ed, we're now alive */
rest_init();
}
-
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