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Subject[RFC][PATCH 12/26] sched, mm: sched_{fork,exec} node assignment
Rework the scheduler fork,exec hooks to allow home-node assignment.

In particular:
- call sched_fork() after the mm is set up and the thread
group list is initialized (such that we can iterate the mm_owner
thread group).
- call sched_exec() after we've got our fresh mm.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
fs/exec.c | 4 ++--
include/linux/sched.h | 4 ++--
kernel/fork.c | 9 +++++----
kernel/sched/core.c | 7 +++++--
kernel/sched/sched.h | 2 ++
5 files changed, 16 insertions(+), 10 deletions(-)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1505,8 +1505,6 @@ static int do_execve_common(const char *
if (IS_ERR(file))
goto out_unmark;

- sched_exec();
-
bprm->file = file;
bprm->filename = filename;
bprm->interp = filename;
@@ -1515,6 +1513,8 @@ static int do_execve_common(const char *
if (retval)
goto out_file;

+ sched_exec(bprm->mm);
+
bprm->argc = count(argv, MAX_ARG_STRINGS);
if ((retval = bprm->argc) < 0)
goto out;
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1999,9 +1999,9 @@ task_sched_runtime(struct task_struct *t

/* sched_exec is called by processes performing an exec */
#ifdef CONFIG_SMP
-extern void sched_exec(void);
+extern void sched_exec(struct mm_struct *mm);
#else
-#define sched_exec() {}
+#define sched_exec(mm) {}
#endif

extern void sched_clock_idle_sleep_event(void);
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1229,9 +1229,6 @@ static struct task_struct *copy_process(
p->memcg_batch.memcg = NULL;
#endif

- /* Perform scheduler related setup. Assign this task to a CPU. */
- sched_fork(p);
-
retval = perf_event_init_task(p);
if (retval)
goto bad_fork_cleanup_policy;
@@ -1284,6 +1281,11 @@ static struct task_struct *copy_process(
* Clear TID on mm_release()?
*/
p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
+
+ INIT_LIST_HEAD(&p->thread_group);
+ /* Perform scheduler related setup. Assign this task to a CPU. */
+ sched_fork(p);
+
#ifdef CONFIG_BLOCK
p->plug = NULL;
#endif
@@ -1326,7 +1328,6 @@ static struct task_struct *copy_process(
* We dont wake it up yet.
*/
p->group_leader = p;
- INIT_LIST_HEAD(&p->thread_group);

/* Now that the task is set up, run cgroup callbacks if
* necessary. We need to run them before the task is visible
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1767,8 +1767,9 @@ void sched_fork(struct task_struct *p)
#ifdef CONFIG_SMP
plist_node_init(&p->pushable_tasks, MAX_PRIO);
#endif
-
put_cpu();
+
+ select_task_node(p, p->mm, SD_BALANCE_FORK);
}

/*
@@ -2507,12 +2508,14 @@ static void update_cpu_load_active(struc
* 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)
+void sched_exec(struct mm_struct *mm)
{
struct task_struct *p = current;
unsigned long flags;
int dest_cpu;

+ select_task_node(p, mm, SD_BALANCE_EXEC);
+
raw_spin_lock_irqsave(&p->pi_lock, flags);
dest_cpu = p->sched_class->select_task_rq(p, SD_BALANCE_EXEC, 0);
if (dest_cpu == smp_processor_id())
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1153,3 +1153,5 @@ enum rq_nohz_flag_bits {

#define nohz_flags(cpu) (&cpu_rq(cpu)->nohz_flags)
#endif
+
+static inline void select_task_node(struct task_struct *p, struct mm_struct *mm, int sd_flags) { }



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