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Subject[PATCH] mm, numa: Do not group on RO pages

Subject: mm, numa: Do not group on RO pages
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri Aug 2 18:38:34 CEST 2013

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.

Sugested-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
include/linux/sched.h | 7 +++++--
kernel/sched/fair.c | 5 +++--
mm/huge_memory.c | 15 +++++++++++++--
mm/memory.c | 31 ++++++++++++++++++++++++++-----
4 files changed, 47 insertions(+), 11 deletions(-)

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1438,12 +1438,15 @@ 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 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 void set_numabalancing_state(bool enabled)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1371,9 +1371,10 @@ void task_numa_free(struct task_struct *
/*
* 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)
@@ -1409,7 +1410,7 @@ void task_numa_fault(int last_cpupid, in
pid = cpupid_to_pid(last_cpupid);

priv = (pid == (p->pid & LAST__PID_MASK));
- if (!priv)
+ if (!priv && !(flags & TNF_NO_GROUP))
task_numa_group(p, cpu, pid);
}

--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1295,6 +1295,7 @@ int do_huge_pmd_numa_page(struct mm_stru
int page_nid = -1, account_nid = -1, this_nid = numa_node_id();
int target_nid, last_cpupid;
bool migrated = false;
+ int flags = 0;

spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(pmd, *pmdp)))
@@ -1333,6 +1334,15 @@ int do_huge_pmd_numa_page(struct mm_stru
account_nid = page_nid = -1; /* someone else took our fault */
goto out_unlock;
}
+
+ /*
+ * 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 (page_mapcount(page) != 1 && !pmd_write(pmd))
+ flags |= TNF_NO_GROUP;
+
spin_unlock(&mm->page_table_lock);

/* Migrate the THP to the requested node */
@@ -1341,7 +1351,8 @@ int do_huge_pmd_numa_page(struct mm_stru
if (!migrated) {
account_nid = -1; /* account against the old page */
goto check_same;
- }
+ } else
+ flags |= TNF_MIGRATED;

page_nid = target_nid;
goto out;
@@ -1364,7 +1375,7 @@ int do_huge_pmd_numa_page(struct mm_stru
if (account_nid == -1)
account_nid = page_nid;
if (account_nid != -1)
- task_numa_fault(last_cpupid, account_nid, HPAGE_PMD_NR, migrated);
+ task_numa_fault(last_cpupid, account_nid, HPAGE_PMD_NR, flags);

return 0;
}
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3537,6 +3537,7 @@ int do_numa_page(struct mm_struct *mm, s
int page_nid = -1, account_nid = -1;
int target_nid, last_cpupid;
bool migrated = false;
+ int flags = 0;

/*
* The "pte" at this point cannot be used safely without
@@ -3569,6 +3570,14 @@ int do_numa_page(struct mm_struct *mm, s
return 0;
}

+ /*
+ * 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 (page_mapcount(page) != 1 && !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, &account_nid);
@@ -3580,14 +3589,16 @@ int do_numa_page(struct mm_struct *mm, s

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

return 0;
}
@@ -3632,6 +3643,7 @@ static int do_pmd_numa_page(struct mm_st
int page_nid = -1, account_nid = -1;
int target_nid;
bool migrated = false;
+ int flags = 0;

if (!pte_present(pteval))
continue;
@@ -3651,6 +3663,14 @@ static int do_pmd_numa_page(struct mm_st
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 (page_mapcount(page) != 1 && !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,
@@ -3659,9 +3679,10 @@ static int do_pmd_numa_page(struct mm_st

if (target_nid != -1) {
migrated = migrate_misplaced_page(page, vma, target_nid);
- if (migrated)
+ if (migrated) {
page_nid = target_nid;
- else
+ flags |= TNF_MIGRATED;
+ } else
account_nid = -1;
} else {
put_page(page);
@@ -3670,7 +3691,7 @@ static int do_pmd_numa_page(struct mm_st
if (account_nid == -1)
account_nid = page_nid;
if (account_nid != -1)
- task_numa_fault(last_cpupid, account_nid, 1, migrated);
+ task_numa_fault(last_cpupid, account_nid, 1, flags);

cond_resched();



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