bacause both mem_cgroup_try_charge and mem_cgroup_try_charg_memcg
do the same thing. mem_cgroup_try_charge tries to safe one css_tryget
because it relies on the fact that the stock consumption disables
preemption while checking the memcg so it either sees an alive memcg or
NULL.
The css_tryget doesn't seem to be a bottleneck anymore (after
per-cpu reference counting has been merged) so let's make the
code simpler and easier to understand and move consume_stock into
__mem_cgroup_try_charge_memcg where it logically belongs.
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
mm/memcontrol.c | 20 ++++----------------
1 file changed, 4 insertions(+), 16 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 509bb59f4744..3f01dc9aa101 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2678,6 +2678,9 @@ static int __mem_cgroup_try_charge_memcg(gfp_t gfp_mask,
if (unlikely(task_in_memcg_oom(current)))
goto nomem;
+ if (consume_stock(memcg, nr_pages))
+ return 0;
+
if (gfp_mask & __GFP_NOFAIL)
oom = false;
@@ -2772,18 +2775,6 @@ static struct mem_cgroup *mem_cgroup_try_charge_mm(struct mm_struct *mm,
rcu_read_unlock();
goto bypass;
}
- if (consume_stock(memcg, nr_pages)) {
- /*
- * It seems dagerous to access memcg without css_get().
- * But considering how consume_stok works, it's not
- * necessary. If consume_stock success, some charges
- * from this memcg are cached on this cpu. So, we
- * don't need to call css_get()/css_tryget() before
- * calling consume_stock().
- */
- rcu_read_unlock();
- goto done;
- }
/* after here, we may be blocked. we need to get refcnt */
} while(!css_tryget(&memcg->css));
rcu_read_unlock();
@@ -2794,7 +2785,7 @@ static struct mem_cgroup *mem_cgroup_try_charge_mm(struct mm_struct *mm,
goto bypass;
else if (ret == -ENOMEM)
memcg = NULL;
-done:
+
return memcg;
bypass:
return root_mem_cgroup;
@@ -2812,9 +2803,6 @@ static int mem_cgroup_try_charge_memcg(gfp_t gfp_mask,
if (mem_cgroup_is_root(memcg) || mem_cgroup_bypass_charge())
return -EINTR;
- if (consume_stock(memcg, nr_pages))
- return 0;
-
return __mem_cgroup_try_charge_memcg(gfp_mask, nr_pages, memcg, oom);
}
--
1.8.4.4
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