Hi Ingo,
What do you think of the following patch? I won't send the
whole series again, I'll queue them up with Andrew if you
think this one looks OK (which is the only major change).
Thanks,
Nick
--
SUSE Labs, Novell Inc.
Consolidate balance-on-exec with balance-on-fork. This is made easy
by the sched-domains RCU patches.
As well as the general goodness of code reduction, this allows
the runqueues to be unlocked during balance-on-fork.
schedstats is a problem. Maybe just have balance-on-event instead
of distinguishing fork and exec?
Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c 2005-04-07 02:39:21.000000000 +1000
+++ linux-2.6/kernel/sched.c 2005-04-07 12:34:06.000000000 +1000
@@ -1022,8 +1022,57 @@ static int find_idlest_cpu(struct sched_
return idlest;
}
+/*
+ * sched_balance_self: balance the current task (running on cpu) in domains
+ * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
+ * SD_BALANCE_EXEC.
+ *
+ * Balance, ie. select the least loaded group.
+ *
+ * Returns the target CPU number, or the same CPU if no balancing is needed.
+ *
+ * preempt must be disabled.
+ */
+static int sched_balance_self(int cpu, int flag)
+{
+ struct task_struct *t = current;
+ struct sched_domain *tmp, *sd = NULL;
-#endif
+ for_each_domain(cpu, tmp)
+ if (tmp->flags & flag)
+ sd = tmp;
+
+ while (sd) {
+ cpumask_t span;
+ struct sched_group *group;
+ int new_cpu;
+
+ span = sd->span;
+ group = find_idlest_group(sd, t, cpu);
+ if (!group)
+ goto nextlevel;
+
+ new_cpu = find_idlest_cpu(group, cpu);
+ if (new_cpu == -1 || new_cpu == cpu)
+ goto nextlevel;
+
+ /* Now try balancing at a lower domain level */
+ cpu = new_cpu;
+nextlevel:
+ sd = NULL;
+ for_each_domain(cpu, tmp) {
+ if (cpus_subset(span, tmp->span))
+ break;
+ if (tmp->flags & flag)
+ sd = tmp;
+ }
+ /* while loop will break here if sd == NULL */
+ }
+
+ return cpu;
+}
+
+#endif /* CONFIG_SMP */
/*
* wake_idle() will wake a task on an idle cpu if task->cpu is
@@ -1241,8 +1290,17 @@ int fastcall wake_up_state(task_t *p, un
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*/
-void fastcall sched_fork(task_t *p)
+void fastcall sched_fork(task_t *p, int clone_flags)
{
+ int cpu = smp_processor_id();
+
+#ifdef CONFIG_SMP
+ preempt_disable();
+ cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
+ preempt_enable();
+#endif
+ set_task_cpu(p, cpu);
+
/*
* We mark the process as running here, but have not actually
* inserted it onto the runqueue yet. This guarantees that
@@ -1303,64 +1361,12 @@ void fastcall wake_up_new_task(task_t *
unsigned long flags;
int this_cpu, cpu;
runqueue_t *rq, *this_rq;
-#ifdef CONFIG_SMP
- struct sched_domain *tmp, *sd = NULL;
-#endif
rq = task_rq_lock(p, &flags);
BUG_ON(p->state != TASK_RUNNING);
this_cpu = smp_processor_id();
cpu = task_cpu(p);
-#ifdef CONFIG_SMP
- for_each_domain(cpu, tmp)
- if (tmp->flags & SD_BALANCE_FORK)
- sd = tmp;
-
- if (sd) {
- cpumask_t span;
- int new_cpu;
- struct sched_group *group;
-
-again:
- schedstat_inc(sd, sbf_cnt);
- span = sd->span;
- cpu = task_cpu(p);
- group = find_idlest_group(sd, p, cpu);
- if (!group) {
- schedstat_inc(sd, sbf_balanced);
- goto nextlevel;
- }
-
- new_cpu = find_idlest_cpu(group, cpu);
- if (new_cpu == -1 || new_cpu == cpu) {
- schedstat_inc(sd, sbf_balanced);
- goto nextlevel;
- }
-
- if (cpu_isset(new_cpu, p->cpus_allowed)) {
- schedstat_inc(sd, sbf_pushed);
- set_task_cpu(p, new_cpu);
- task_rq_unlock(rq, &flags);
- rq = task_rq_lock(p, &flags);
- cpu = task_cpu(p);
- }
-
- /* Now try balancing at a lower domain level */
-nextlevel:
- sd = NULL;
- for_each_domain(cpu, tmp) {
- if (cpus_subset(span, tmp->span))
- break;
- if (tmp->flags & SD_BALANCE_FORK)
- sd = tmp;
- }
-
- if (sd)
- goto again;
- }
-
-#endif
/*
* We decrease the sleep average of forking parents
* and children as well, to keep max-interactive tasks
@@ -1708,59 +1714,17 @@ out:
task_rq_unlock(rq, &flags);
}
-/*
- * sched_exec(): find the highest-level, exec-balance-capable
- * domain and try to migrate the task to the least loaded CPU.
- *
- * execve() is a valuable balancing opportunity, because at this point
- * the task has the smallest effective memory and cache footprint.
+/*
+ * sched_exec - execve() is a valuable balancing opportunity, because at
+ * this point the task has the smallest effective memory and cache footprint.
*/
void sched_exec(void)
{
- struct sched_domain *tmp, *sd = NULL;
int new_cpu, this_cpu = get_cpu();
-
- for_each_domain(this_cpu, tmp)
- if (tmp->flags & SD_BALANCE_EXEC)
- sd = tmp;
-
- if (sd) {
- cpumask_t span;
- struct sched_group *group;
-again:
- schedstat_inc(sd, sbe_cnt);
- span = sd->span;
- group = find_idlest_group(sd, current, this_cpu);
- if (!group) {
- schedstat_inc(sd, sbe_balanced);
- goto nextlevel;
- }
- new_cpu = find_idlest_cpu(group, this_cpu);
- if (new_cpu == -1 || new_cpu == this_cpu) {
- schedstat_inc(sd, sbe_balanced);
- goto nextlevel;
- }
-
- schedstat_inc(sd, sbe_pushed);
- put_cpu();
- sched_migrate_task(current, new_cpu);
-
- /* Now try balancing at a lower domain level */
- this_cpu = get_cpu();
-nextlevel:
- sd = NULL;
- for_each_domain(this_cpu, tmp) {
- if (cpus_subset(span, tmp->span))
- break;
- if (tmp->flags & SD_BALANCE_EXEC)
- sd = tmp;
- }
-
- if (sd)
- goto again;
- }
-
+ new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
put_cpu();
+ if (new_cpu != this_cpu)
+ sched_migrate_task(current, new_cpu);
}
/*
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h 2005-04-07 02:31:47.000000000
+1000
+++ linux-2.6/include/linux/sched.h 2005-04-07 02:39:21.000000000 +1000
@@ -923,7 +923,7 @@ extern void FASTCALL(wake_up_new_task(st
#else
static inline void kick_process(struct task_struct *tsk) { }
#endif
-extern void FASTCALL(sched_fork(task_t * p));
+extern void FASTCALL(sched_fork(task_t * p, int clone_flags));
extern void FASTCALL(sched_exit(task_t * p));
extern int in_group_p(gid_t);
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c 2005-04-07 02:31:47.000000000 +1000
+++ linux-2.6/kernel/fork.c 2005-04-07 02:39:21.000000000 +1000
@@ -1000,9 +1000,6 @@ static task_t *copy_process(unsigned lon
p->pdeath_signal = 0;
p->exit_state = 0;
- /* Perform scheduler related setup */
- sched_fork(p);
-
/*
* Ok, make it visible to the rest of the system.
* We dont wake it up yet.
@@ -1011,19 +1008,25 @@ static task_t *copy_process(unsigned lon
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
+ /* Perform scheduler related setup. Assign this task to a CPU. */
+ sched_fork(p, clone_flags);
+
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);
/*
- * The task hasn't been attached yet, so cpus_allowed mask cannot
- * have changed. The cpus_allowed mask of the parent may have
- * changed after it was copied first time, and it may then move to
- * another CPU - so we re-copy it here and set the child's CPU to
- * the parent's CPU. This avoids alot of nasty races.
+ * The task hasn't been attached yet, so its cpus_allowed mask will
+ * not be changed, nor will its assigned CPU.
+ *
+ * The cpus_allowed mask of the parent may have changed after it was
+ * copied first time - so re-copy it here, then check the child's CPU
+ * to ensure it is on a valid CPU (and if not, just force it back to
+ * parent's CPU). This avoids alot of nasty races.
*/
p->cpus_allowed = current->cpus_allowed;
- set_task_cpu(p, smp_processor_id());
-
+ if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed)))
+ set_task_cpu(p, smp_processor_id());
+
/*
* Check for pending SIGKILL! The new thread should not be allowed
* to slip out of an OOM kill. (or normal SIGKILL.)
