The patch titled
Subject: mm: memcg: relayout structure mem_cgroup to avoid cache interference
has been added to the -mm tree. Its filename is
mm-memcg-relayout-structure-mem_cgroup-to-avoid-cache-interfereing.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-relayout-structure-mem_cgroup-to-avoid-cache-interfereing.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-relayout-structure-mem_cgroup-to-avoid-cache-interfereing.patch
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------------------------------------------------------
From: Feng Tang <feng.tang@xxxxxxxxx>
Subject: mm: memcg: relayout structure mem_cgroup to avoid cache interference
0day reported one -22.7% regression for will-it-scale page_fault2 case [1]
on a 4 sockets 144 CPU platform, and bisected to it to be caused by
Waiman's optimization (commit bd0b230fe1) of saving one 'struct
page_counter' space for 'struct mem_cgroup'.
Initially we thought it was due to the cache alignment change introduced
by the patch, but further debug shows that it is due to some hot data
members ('vmstats_local', 'vmstats_percpu', 'vmstats') sit in 2 adjacent
cacheline (2N and 2N+1 cacheline), and when adjacent cache line prefetch
is enabled, it triggers an "extended level" of cache false sharing for 2
adjacent cache lines.
So exchange the 2 member blocks, while keeping mostly the original cache
alignment, which can restore and even enhance the performance, and save 64
bytes of space for 'struct mem_cgroup' (from 2880 to 2816, with 0day's
default RHEL-8.3 kernel config)
[1]. https://lore.kernel.org/lkml/20201102091543.GM31092@shao2-debian/
Link: https://lkml.kernel.org/r/20201125062445.GA51005@xxxxxxxxxxxxxxxxxxxxxxx
Fixes: bd0b230fe145 ("mm/memcg: unify swap and memsw page counters")
Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Xing Zhengjun <zhengjun.xing@xxxxxxxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Chris Down <chris@xxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)
--- a/include/linux/memcontrol.h~mm-memcg-relayout-structure-mem_cgroup-to-avoid-cache-interfereing
+++ a/include/linux/memcontrol.h
@@ -282,20 +282,6 @@ struct mem_cgroup {
MEMCG_PADDING(_pad1_);
- /*
- * set > 0 if pages under this cgroup are moving to other cgroup.
- */
- atomic_t moving_account;
- struct task_struct *move_lock_task;
-
- /* Legacy local VM stats and events */
- struct memcg_vmstats_percpu __percpu *vmstats_local;
-
- /* Subtree VM stats and events (batched updates) */
- struct memcg_vmstats_percpu __percpu *vmstats_percpu;
-
- MEMCG_PADDING(_pad2_);
-
atomic_long_t vmstats[MEMCG_NR_STAT];
atomic_long_t vmevents[NR_VM_EVENT_ITEMS];
@@ -317,6 +303,20 @@ struct mem_cgroup {
struct list_head objcg_list; /* list of inherited objcgs */
#endif
+ MEMCG_PADDING(_pad2_);
+
+ /*
+ * set > 0 if pages under this cgroup are moving to other cgroup.
+ */
+ atomic_t moving_account;
+ struct task_struct *move_lock_task;
+
+ /* Legacy local VM stats and events */
+ struct memcg_vmstats_percpu __percpu *vmstats_local;
+
+ /* Subtree VM stats and events (batched updates) */
+ struct memcg_vmstats_percpu __percpu *vmstats_percpu;
+
#ifdef CONFIG_CGROUP_WRITEBACK
struct list_head cgwb_list;
struct wb_domain cgwb_domain;
_
Patches currently in -mm which might be from feng.tang@xxxxxxxxx are
mm-memcg-relayout-structure-mem_cgroup-to-avoid-cache-interfereing.patch
