Hi,
I know we have many works to be done: THP, dirty limit, per-memcg background reclaim.
So, I'm not in hurry to push this patch.
This patch add checks at allocating or freeing a page whether the page is used
(iow, charged) from the view point of memcg. In fact, I've hit this check while
debugging a problem on RHEL6 kernel, which have stuck me these days and have not
been fixed unfortunately...
===
From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
This patch add checks at allocating or freeing a page whether the page is used
(iow, charged) from the view point of memcg.
This check may be usefull in debugging a problem and we did a similar checks
before the commit 52d4b9ac(memcg: allocate all page_cgroup at boot).
This patch adds some overheads at allocating or freeing memory, so it's enabled
only when CONFIG_DEBUG_VM is enabled.
Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 12 +++++++++++
mm/memcontrol.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
mm/page_alloc.c | 8 +++++-
3 files changed, 65 insertions(+), 2 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 067115c..04754c4 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -146,6 +146,8 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
gfp_t gfp_mask);
u64 mem_cgroup_get_limit(struct mem_cgroup *mem);
+bool mem_cgroup_bad_page_check(struct page *page);
+void mem_cgroup_print_bad_page(struct page *page);
#else /* CONFIG_CGROUP_MEM_RES_CTLR */
struct mem_cgroup;
@@ -336,6 +338,16 @@ u64 mem_cgroup_get_limit(struct mem_cgroup *mem)
return 0;
}
+static inline bool
+mem_cgroup_bad_page_check(struct page *page)
+{
+ return false;
+}
+
+static void
+mem_cgroup_print_bad_page(struct page *page)
+{
+}
#endif /* CONFIG_CGROUP_MEM_CONT */
#endif /* _LINUX_MEMCONTROL_H */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7d89517..21af8b2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2971,6 +2971,53 @@ int mem_cgroup_shmem_charge_fallback(struct page *page,
return ret;
}
+#ifdef CONFIG_DEBUG_VM
+static bool
+__mem_cgroup_bad_page_check(struct page *page, struct page_cgroup **pcp)
+{
+ struct page_cgroup *pc;
+ bool ret = false;
+
+ pc = lookup_page_cgroup(page);
+ if (unlikely(!pc))
+ goto out;
+
+ if (PageCgroupUsed(pc)) {
+ ret = true;
+ if (pcp)
+ *pcp = pc;
+ }
+out:
+ return ret;
+}
+
+bool mem_cgroup_bad_page_check(struct page *page)
+{
+ if (mem_cgroup_disabled())
+ return false;
+
+ return __mem_cgroup_bad_page_check(page, NULL);
+}
+
+void mem_cgroup_print_bad_page(struct page *page)
+{
+ struct page_cgroup *pc;
+
+ if (__mem_cgroup_bad_page_check(page, &pc))
+ printk(KERN_ALERT "pc:%p pc->flags:%ld pc->mem_cgroup:%p\n",
+ pc, pc->flags, pc->mem_cgroup);
+}
+#else
+bool mem_cgroup_bad_page_check(struct page *page)
+{
+ return false;
+}
+
+void mem_cgroup_print_bad_page(struct page *page)
+{
+}
+#endif
+
static DEFINE_MUTEX(set_limit_mutex);
static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7650ceb..5caeda8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -53,6 +53,7 @@
#include <linux/compaction.h>
#include <trace/events/kmem.h>
#include <linux/ftrace_event.h>
+#include <linux/memcontrol.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -570,7 +571,8 @@ static inline int free_pages_check(struct page *page)
if (unlikely(page_mapcount(page) |
(page->mapping != NULL) |
(atomic_read(&page->_count) != 0) |
- (page->flags & PAGE_FLAGS_CHECK_AT_FREE))) {
+ (page->flags & PAGE_FLAGS_CHECK_AT_FREE) |
+ (mem_cgroup_bad_page_check(page)))) {
bad_page(page);
return 1;
}
@@ -755,7 +757,8 @@ static inline int check_new_page(struct page *page)
if (unlikely(page_mapcount(page) |
(page->mapping != NULL) |
(atomic_read(&page->_count) != 0) |
- (page->flags & PAGE_FLAGS_CHECK_AT_PREP))) {
+ (page->flags & PAGE_FLAGS_CHECK_AT_PREP) |
+ (mem_cgroup_bad_page_check(page)))) {
bad_page(page);
return 1;
}
@@ -5627,4 +5630,5 @@ void dump_page(struct page *page)
page, atomic_read(&page->_count), page_mapcount(page),
page->mapping, page->index);
dump_page_flags(page->flags);
+ mem_cgroup_print_bad_page(page);
}
--
1.7.1
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