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sched/numa: Be more careful about joining numa groups 

Due to the way the pid is truncated, and tasks are moved between
CPUs by the scheduler, it is possible for the current task_numa_fault
to group together tasks that do not actually share memory together.

This patch adds a few easy sanity checks to task_numa_fault, joining
tasks together if they share the same tsk->mm, or if the fault was on
a page with an elevated mapcount, in a shared VMA.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-57-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Rik van Riel 2013-10-07 11:29:34 +01:00 committed by Ingo Molnar
parent 0ec8aa00f2
commit dabe1d9924
3 changed files with 19 additions and 5 deletions
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1
include/linux/sched.h
View File

@ -1454,6 +1454,7 @@ struct task_struct {
#define TNF_MIGRATED 0x01
#define TNF_NO_GROUP 0x02
#define TNF_SHARED 0x04
#ifdef CONFIG_NUMA_BALANCING
extern void task_numa_fault(int last_node, int node, int pages, int flags);

16
kernel/sched/fair.c
View File

@ -1381,7 +1381,7 @@ static void double_lock(spinlock_t *l1, spinlock_t *l2)
spin_lock_nested(l2, SINGLE_DEPTH_NESTING);
}
static void task_numa_group(struct task_struct *p, int cpupid)
static void task_numa_group(struct task_struct *p, int cpupid, int flags)
{
struct numa_group *grp, *my_grp;
struct task_struct *tsk;
@ -1439,11 +1439,17 @@ static void task_numa_group(struct task_struct *p, int cpupid)
if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
goto unlock;
if (!get_numa_group(grp))
goto unlock;
/* Always join threads in the same process. */
if (tsk->mm == current->mm)
join = true;
/* Simple filter to avoid false positives due to PID collisions */
if (flags & TNF_SHARED)
join = true;
if (join && !get_numa_group(grp))
join = false;
unlock:
rcu_read_unlock();
@ -1539,7 +1545,7 @@ void task_numa_fault(int last_cpupid, int node, int pages, int flags)
} else {
priv = cpupid_match_pid(p, last_cpupid);
if (!priv && !(flags & TNF_NO_GROUP))
task_numa_group(p, last_cpupid);
task_numa_group(p, last_cpupid, flags);
}
/*

7
mm/memory.c
View File

@ -3584,6 +3584,13 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (!pte_write(pte))
flags |= TNF_NO_GROUP;
/*
* Flag if the page is shared between multiple address spaces. This
* is later used when determining whether to group tasks together
*/
if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
flags |= TNF_SHARED;
last_cpupid = page_cpupid_last(page);
page_nid = page_to_nid(page);
target_nid = numa_migrate_prep(page, vma, addr, page_nid);