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Subject[PATCH 46/63] mm: numa: Do not group on RO pages
Date
From: Peter Zijlstra <peterz@infradead.org>

And here's a little something to make sure not the whole world ends up
in a single group.

As while we don't migrate shared executable pages, we do scan/fault on
them. And since everybody links to libc, everybody ends up in the same
group.

[riel@redhat.com: mapcount 1]
Suggested-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
include/linux/sched.h | 7 +++++--
kernel/sched/fair.c | 5 +++--
mm/huge_memory.c | 15 +++++++++++++--
mm/memory.c | 30 ++++++++++++++++++++++++++----
4 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4fad1f17..15888f5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1434,13 +1434,16 @@ struct task_struct {
/* Future-safe accessor for struct task_struct's cpus_allowed. */
#define tsk_cpus_allowed(tsk) (&(tsk)->cpus_allowed)

+#define TNF_MIGRATED 0x01
+#define TNF_NO_GROUP 0x02
+
#ifdef CONFIG_NUMA_BALANCING
-extern void task_numa_fault(int last_node, int node, int pages, bool migrated);
+extern void task_numa_fault(int last_node, int node, int pages, int flags);
extern pid_t task_numa_group_id(struct task_struct *p);
extern void set_numabalancing_state(bool enabled);
#else
static inline void task_numa_fault(int last_node, int node, int pages,
- bool migrated)
+ int flags)
{
}
static inline pid_t task_numa_group_id(struct task_struct *p)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index abdbb7c..896cf87 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1361,9 +1361,10 @@ void task_numa_free(struct task_struct *p)
/*
* Got a PROT_NONE fault for a page on @node.
*/
-void task_numa_fault(int last_cpupid, int node, int pages, bool migrated)
+void task_numa_fault(int last_cpupid, int node, int pages, int flags)
{
struct task_struct *p = current;
+ bool migrated = flags & TNF_MIGRATED;
int priv;

if (!numabalancing_enabled)
@@ -1394,7 +1395,7 @@ void task_numa_fault(int last_cpupid, int node, int pages, bool migrated)
priv = 1;
} else {
priv = cpupid_match_pid(p, last_cpupid);
- if (!priv)
+ if (!priv && !(flags & TNF_NO_GROUP))
task_numa_group(p, last_cpupid);
}

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 048d4b2..aaf46dc 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1297,6 +1297,7 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
int target_nid, last_cpupid = -1;
bool page_locked;
bool migrated = false;
+ int flags = 0;

spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(pmd, *pmdp)))
@@ -1311,6 +1312,14 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);

/*
+ * Avoid grouping on DSO/COW pages in specific and RO pages
+ * in general, RO pages shouldn't hurt as much anyway since
+ * they can be in shared cache state.
+ */
+ if (!pmd_write(pmd))
+ flags |= TNF_NO_GROUP;
+
+ /*
* Acquire the page lock to serialise THP migrations but avoid dropping
* page_table_lock if at all possible
*/
@@ -1355,8 +1364,10 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
spin_unlock(&mm->page_table_lock);
migrated = migrate_misplaced_transhuge_page(mm, vma,
pmdp, pmd, addr, page, target_nid);
- if (migrated)
+ if (migrated) {
+ flags |= TNF_MIGRATED;
page_nid = target_nid;
+ }

goto out;
clear_pmdnuma:
@@ -1374,7 +1385,7 @@ out:
page_unlock_anon_vma_read(anon_vma);

if (page_nid != -1)
- task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, migrated);
+ task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);

return 0;
}
diff --git a/mm/memory.c b/mm/memory.c
index f779403..1aa4187 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3558,6 +3558,7 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
int last_cpupid;
int target_nid;
bool migrated = false;
+ int flags = 0;

/*
* The "pte" at this point cannot be used safely without
@@ -3586,6 +3587,14 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
}
BUG_ON(is_zero_pfn(page_to_pfn(page)));

+ /*
+ * Avoid grouping on DSO/COW pages in specific and RO pages
+ * in general, RO pages shouldn't hurt as much anyway since
+ * they can be in shared cache state.
+ */
+ if (!pte_write(pte))
+ flags |= TNF_NO_GROUP;
+
last_cpupid = page_cpupid_last(page);
page_nid = page_to_nid(page);
target_nid = numa_migrate_prep(page, vma, addr, page_nid);
@@ -3597,12 +3606,14 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

/* Migrate to the requested node */
migrated = migrate_misplaced_page(page, vma, target_nid);
- if (migrated)
+ if (migrated) {
page_nid = target_nid;
+ flags |= TNF_MIGRATED;
+ }

out:
if (page_nid != -1)
- task_numa_fault(last_cpupid, page_nid, 1, migrated);
+ task_numa_fault(last_cpupid, page_nid, 1, flags);
return 0;
}

@@ -3643,6 +3654,7 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
int page_nid = -1;
int target_nid;
bool migrated = false;
+ int flags = 0;

if (!pte_present(pteval))
continue;
@@ -3662,20 +3674,30 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (unlikely(!page))
continue;

+ /*
+ * Avoid grouping on DSO/COW pages in specific and RO pages
+ * in general, RO pages shouldn't hurt as much anyway since
+ * they can be in shared cache state.
+ */
+ if (!pte_write(pteval))
+ flags |= TNF_NO_GROUP;
+
last_cpupid = page_cpupid_last(page);
page_nid = page_to_nid(page);
target_nid = numa_migrate_prep(page, vma, addr, page_nid);
pte_unmap_unlock(pte, ptl);
if (target_nid != -1) {
migrated = migrate_misplaced_page(page, vma, target_nid);
- if (migrated)
+ if (migrated) {
page_nid = target_nid;
+ flags |= TNF_MIGRATED;
+ }
} else {
put_page(page);
}

if (page_nid != -1)
- task_numa_fault(last_cpupid, page_nid, 1, migrated);
+ task_numa_fault(last_cpupid, page_nid, 1, flags);

pte = pte_offset_map_lock(mm, pmdp, addr, &ptl);
}
--
1.8.1.4


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