Commit-ID: dabe1d992414a6456e60e41f1d1ad8affc6d444d Gitweb: http://git.kernel.org/tip/dabe1d992414a6456e60e41f1d1ad8affc6d444d Author: Rik van Riel <r...@redhat.com> AuthorDate: Mon, 7 Oct 2013 11:29:34 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 9 Oct 2013 14:48:12 +0200
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 <r...@redhat.com> Signed-off-by: Mel Gorman <mgor...@suse.de> Cc: Andrea Arcangeli <aarca...@redhat.com> Cc: Johannes Weiner <han...@cmpxchg.org> Cc: Srikar Dronamraju <sri...@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <pet...@infradead.org> Link: http://lkml.kernel.org/r/1381141781-10992-57-git-send-email-mgor...@suse.de Signed-off-by: Ingo Molnar <mi...@kernel.org> --- include/linux/sched.h | 1 + kernel/sched/fair.c | 16 +++++++++++----- mm/memory.c | 7 +++++++ 3 files changed, 19 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 1127a46..59f953b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -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); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 5166b9b..222c2d0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -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; + + /* Simple filter to avoid false positives due to PID collisions */ + if (flags & TNF_SHARED) + join = true; - 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); } /* diff --git a/mm/memory.c b/mm/memory.c index 9898eeb..823720c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
