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Subject[BUGFIX][PATCH 1/4] memcg: fix limit estimation at reclaim for hugepage
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Current memory cgroup's code tends to assume page_size == PAGE_SIZE
and arrangement for THP is not enough yet.

This is one of fixes for supporing THP. This adds
mem_cgroup_check_margin() and checks whether there are required amount of
free resource after memory reclaim. By this, THP page allocation
can know whether it really succeeded or not and avoid infinite-loop
and hangup.

Total fixes for do_charge()/reclaim memory will follow this patch.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
include/linux/res_counter.h | 11 +++++++++++
mm/memcontrol.c | 25 ++++++++++++++++++++++++-
2 files changed, 35 insertions(+), 1 deletion(-)

Index: mmotm-0125/include/linux/res_counter.h
===================================================================
--- mmotm-0125.orig/include/linux/res_counter.h
+++ mmotm-0125/include/linux/res_counter.h
@@ -182,6 +182,17 @@ static inline bool res_counter_check_und
return ret;
}

+static inline s64 res_counter_check_margin(struct res_counter *cnt)
+{
+ s64 ret;
+ unsigned long flags;
+
+ spin_lock_irqsave(&cnt->lock, flags);
+ ret = cnt->limit - cnt->usage;
+ spin_unlock_irqrestore(&cnt->lock, flags);
+ return ret;
+}
+
static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
{
bool ret;
Index: mmotm-0125/mm/memcontrol.c
===================================================================
--- mmotm-0125.orig/mm/memcontrol.c
+++ mmotm-0125/mm/memcontrol.c
@@ -1111,6 +1111,22 @@ static bool mem_cgroup_check_under_limit
return false;
}

+static s64 mem_cgroup_check_margin(struct mem_cgroup *mem)
+{
+ s64 mem_margin;
+
+ if (do_swap_account) {
+ s64 memsw_margin;
+
+ mem_margin = res_counter_check_margin(&mem->res);
+ memsw_margin = res_counter_check_margin(&mem->memsw);
+ if (mem_margin > memsw_margin)
+ mem_margin = memsw_margin;
+ } else
+ mem_margin = res_counter_check_margin(&mem->res);
+ return mem_margin;
+}
+
static unsigned int get_swappiness(struct mem_cgroup *memcg)
{
struct cgroup *cgrp = memcg->css.cgroup;
@@ -1853,7 +1869,14 @@ static int __mem_cgroup_do_charge(struct
* Check the limit again to see if the reclaim reduced the
* current usage of the cgroup before giving up
*/
- if (ret || mem_cgroup_check_under_limit(mem_over_limit))
+ if (mem_cgroup_check_margin(mem_over_limit) >= csize)
+ return CHARGE_RETRY;
+
+ /*
+ * If the charge size is a PAGE_SIZE, it's not hopeless while
+ * we can reclaim a page.
+ */
+ if (csize == PAGE_SIZE && ret)
return CHARGE_RETRY;

/*


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