From: Waiman Long <longman@xxxxxxxxxx> Subject: mm/memcg: unify swap and memsw page counters The swap page counter is v2 only while memsw is v1 only. As v1 and v2 controllers cannot be active at the same time, there is no point to keep both swap and memsw page counters in mem_cgroup. The previous patch has made sure that memsw page counter is updated and accessed only when in v1 code paths. So it is now safe to alias the v1 memsw page counter to v2 swap page counter. This saves 14 long's in the size of mem_cgroup. This is a saving of 112 bytes for 64-bit archs. While at it, also document which page counters are used in v1 and/or v2. Link: https://lkml.kernel.org/r/20200914024452.19167-4-longman@xxxxxxxxxx Signed-off-by: Waiman Long <longman@xxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> 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> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/memcontrol.h | 13 ++++++++----- mm/memcontrol.c | 3 --- 2 files changed, 8 insertions(+), 8 deletions(-) --- a/include/linux/memcontrol.h~mm-memcg-unify-swap-and-memsw-page-counters +++ a/include/linux/memcontrol.h @@ -215,13 +215,16 @@ struct mem_cgroup { struct mem_cgroup_id id; /* Accounted resources */ - struct page_counter memory; - struct page_counter swap; + struct page_counter memory; /* Both v1 & v2 */ + + union { + struct page_counter swap; /* v2 only */ + struct page_counter memsw; /* v1 only */ + }; /* Legacy consumer-oriented counters */ - struct page_counter memsw; - struct page_counter kmem; - struct page_counter tcpmem; + struct page_counter kmem; /* v1 only */ + struct page_counter tcpmem; /* v1 only */ /* Range enforcement for interrupt charges */ struct work_struct high_work; --- a/mm/memcontrol.c~mm-memcg-unify-swap-and-memsw-page-counters +++ a/mm/memcontrol.c @@ -5295,13 +5295,11 @@ mem_cgroup_css_alloc(struct cgroup_subsy memcg->use_hierarchy = true; page_counter_init(&memcg->memory, &parent->memory); page_counter_init(&memcg->swap, &parent->swap); - page_counter_init(&memcg->memsw, &parent->memsw); page_counter_init(&memcg->kmem, &parent->kmem); page_counter_init(&memcg->tcpmem, &parent->tcpmem); } else { page_counter_init(&memcg->memory, NULL); page_counter_init(&memcg->swap, NULL); - page_counter_init(&memcg->memsw, NULL); page_counter_init(&memcg->kmem, NULL); page_counter_init(&memcg->tcpmem, NULL); /* @@ -5430,7 +5428,6 @@ static void mem_cgroup_css_reset(struct page_counter_set_max(&memcg->memory, PAGE_COUNTER_MAX); page_counter_set_max(&memcg->swap, PAGE_COUNTER_MAX); - page_counter_set_max(&memcg->memsw, PAGE_COUNTER_MAX); page_counter_set_max(&memcg->kmem, PAGE_COUNTER_MAX); page_counter_set_max(&memcg->tcpmem, PAGE_COUNTER_MAX); page_counter_set_min(&memcg->memory, 0); _
