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SubjectRe: [PATCH 00/31] numa/core patches
On Fri, Oct 26, 2012 at 11:08:00AM +0200, Peter Zijlstra wrote:
> On Fri, 2012-10-26 at 17:07 +0800, Zhouping Liu wrote:
> > [ 180.918591] RIP: 0010:[<ffffffff8118c39a>] [<ffffffff8118c39a>] mem_cgroup_prepare_migration+0xba/0xd0
>
> > [ 182.681450] [<ffffffff81183b60>] do_huge_pmd_numa_page+0x180/0x500
> > [ 182.775090] [<ffffffff811585c9>] handle_mm_fault+0x1e9/0x360
> > [ 182.863038] [<ffffffff81632b62>] __do_page_fault+0x172/0x4e0
> > [ 182.950574] [<ffffffff8101c283>] ? __switch_to_xtra+0x163/0x1a0
> > [ 183.041512] [<ffffffff8101281e>] ? __switch_to+0x3ce/0x4a0
> > [ 183.126832] [<ffffffff8162d686>] ? __schedule+0x3c6/0x7a0
> > [ 183.211216] [<ffffffff81632ede>] do_page_fault+0xe/0x10
> > [ 183.293705] [<ffffffff8162f518>] page_fault+0x28/0x30
>
> Johannes, this looks like the thp migration memcg hookery gone bad,
> could you have a look at this?

Oops. Here is an incremental fix, feel free to fold it into #31.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5c30a14..0d7ebd3 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -801,8 +801,6 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (!new_page)
goto alloc_fail;

- mem_cgroup_prepare_migration(page, new_page, &memcg);
-
lru = PageLRU(page);

if (lru && isolate_lru_page(page)) /* does an implicit get_page() */
@@ -835,6 +833,14 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

return;
}
+ /*
+ * Traditional migration needs to prepare the memcg charge
+ * transaction early to prevent the old page from being
+ * uncharged when installing migration entries. Here we can
+ * save the potential rollback and start the charge transfer
+ * only when migration is already known to end successfully.
+ */
+ mem_cgroup_prepare_migration(page, new_page, &memcg);

entry = mk_pmd(new_page, vma->vm_page_prot);
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
@@ -845,6 +851,12 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
set_pmd_at(mm, haddr, pmd, entry);
update_mmu_cache_pmd(vma, address, entry);
page_remove_rmap(page);
+ /*
+ * Finish the charge transaction under the page table lock to
+ * prevent split_huge_page() from dividing up the charge
+ * before it's fully transferred to the new page.
+ */
+ mem_cgroup_end_migration(memcg, page, new_page, true);
spin_unlock(&mm->page_table_lock);

put_page(page); /* Drop the rmap reference */
@@ -856,18 +868,14 @@ void do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

unlock_page(new_page);

- mem_cgroup_end_migration(memcg, page, new_page, true);
-
unlock_page(page);
put_page(page); /* Drop the local reference */

return;

alloc_fail:
- if (new_page) {
- mem_cgroup_end_migration(memcg, page, new_page, false);
+ if (new_page)
put_page(new_page);
- }

unlock_page(page);

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7acf43b..011e510 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3255,15 +3255,18 @@ void mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
struct mem_cgroup **memcgp)
{
struct mem_cgroup *memcg = NULL;
+ unsigned int nr_pages = 1;
struct page_cgroup *pc;
enum charge_type ctype;

*memcgp = NULL;

- VM_BUG_ON(PageTransHuge(page));
if (mem_cgroup_disabled())
return;

+ if (PageTransHuge(page))
+ nr_pages <<= compound_order(page);
+
pc = lookup_page_cgroup(page);
lock_page_cgroup(pc);
if (PageCgroupUsed(pc)) {
@@ -3325,7 +3328,7 @@ void mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
* charged to the res_counter since we plan on replacing the
* old one and only one page is going to be left afterwards.
*/
- __mem_cgroup_commit_charge(memcg, newpage, 1, ctype, false);
+ __mem_cgroup_commit_charge(memcg, newpage, nr_pages, ctype, false);
}

/* remove redundant charge if migration failed*/

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