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sched/numa: Be more careful about joining numa groups

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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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16
kernel/sched/fair.c
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@@ -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;
@@ -1439,10 +1439,16 @@ 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;
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);
}
/*