Tags Tags

[PATCH 1/3] mm: add rss counters consistency check

January 06th, 2012 - 12:40 pm ET by Konstantin Khlebnikov | Report spam
Help Create a new topic
This patch warn about non-zero rss counters at final mmdrop.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>

kernel/fork.c | 21 ++++++++++++++++++
1 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index da4a6a1..67a79dd 100644
a/kernel/fork.c
+++ b/kernel/fork.c
@@ -507,6 +507,23 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
return NULL;
}

+static void check_mm(struct mm_struct *mm)
+{
+ int i;
+
+ for (i = 0; i < NR_MM_COUNTERS; i++) {
+ long x = atomic_long_read(&mm->rss_stat.count[i]);
+
+ if (unlikely(x))
+ printk(KERN_ALERT "BUG: Bad rss-counter state "
+ "mm:%p idx:%d val:%ld", mm, i, x);
+ }
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ VM_BUG_ON(mm->pmd_huge_pte);
+#endif
+}
+
/*
* Allocate and initialize an mm_struct.
*/
@@ -534,9 +551,7 @@ void __mmdrop(struct mm_struct *mm)
mm_free_pgd(mm);
destroy_context(mm);
mmu_notifier_mm_destroy(mm);
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- VM_BUG_ON(mm->pmd_huge_pte);
-#endif
+ check_mm(mm);
free_mm(mm);
}
EXPORT_SYMBOL_GPL(__mmdrop);

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
email Follow the discussionReplies 8 repliesReplies Make a reply

Replies

#1 KAMEZAWA Hiroyuki
January 11th, 2012 - 12:50 am ET | Report spam
On Fri, 06 Jan 2012 21:38:56 +0400
Konstantin Khlebnikov wrote:

Memory migration fill pte with migration entry and it didn't update rss counters.
Then it replace migration entry with new page (or old one if migration was failed).
But between this two passes this pte can be unmaped, or task can fork child and
it will get copy of this migration entry. Nobody account this into rss counters.

This patch properly adjust rss counters for migration entries in zap_pte_range()
and copy_one_pte(). Thus we avoid extra atomic operations on migration fast-path.

Signed-off-by: Konstantin Khlebnikov



It's better to show wheter this is a bug-fix or not in changelog.

IIUC, the bug-fix is the 1st harf of this patch + patch [2/3].
Your new bug-check code is in patch[1/3] and 2nd half of this patch.

I think it's better to do bug-fix 1st and add bug-check later.

So, could you reorder patches to bug-fix and new-bug-check ?

To the logic itself,
Acked-by: KAMEZAWA Hiroyuki
Please CC when you repost.




mm/memory.c | 37 ++++++++++++++++++++++++++++
1 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 829d437..2f96ffc 100644
a/mm/memory.c
+++ b/mm/memory.c
@@ -878,15 +878,24 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
}
if (likely(!non_swap_entry(entry)))
rss[MM_SWAPENTS]++;
- else if (is_write_migration_entry(entry) &&
- is_cow_mapping(vm_flags)) {
- /*
- * COW mappings require pages in both parent
- * and child to be set to read.
- */
- make_migration_entry_read(&entry);
- pte = swp_entry_to_pte(entry);
- set_pte_at(src_mm, addr, src_pte, pte);
+ else if (is_migration_entry(entry)) {
+ page = migration_entry_to_page(entry);
+
+ if (PageAnon(page))
+ rss[MM_ANONPAGES]++;
+ else
+ rss[MM_FILEPAGES]++;
+
+ if (is_write_migration_entry(entry) &&
+ is_cow_mapping(vm_flags)) {
+ /*
+ * COW mappings require pages in both
+ * parent and child to be set to read.
+ */
+ make_migration_entry_read(&entry);
+ pte = swp_entry_to_pte(entry);
+ set_pte_at(src_mm, addr, src_pte, pte);
+ }
}
}
goto out_set_pte;
@@ -1191,6 +1200,16 @@ again:

if (!non_swap_entry(entry))
rss[MM_SWAPENTS]--;
+ else if (is_migration_entry(entry)) {
+ struct page *page;
+
+ page = migration_entry_to_page(entry);
+
+ if (PageAnon(page))
+ rss[MM_ANONPAGES]--;
+ else
+ rss[MM_FILEPAGES]--;
+ }
if (unlikely(!free_swap_and_cache(entry)))
print_bad_pte(vma, addr, ptent, NULL);
}

To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:""> </a>




To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Similar topics

Make your own search :