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Date: Wed, 22 Oct 2014 17:46:06 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>,
Vladimir Davydov <vdavydov@...allels.com>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 2/4] mm: memcontrol: remove unnecessary PCG_MEMSW
memory+swap charge flag
On Mon 20-10-14 11:22:10, Johannes Weiner wrote:
> Now that mem_cgroup_swapout() fully uncharges the page, every page
> that is still in use when reaching mem_cgroup_uncharge() is known to
> carry both the memory and the memory+swap charge. Simplify the
> uncharge path and remove the PCG_MEMSW page flag accordingly.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Looks good
Acked-by: Michal Hocko <mhocko@...e.cz>
> ---
> include/linux/page_cgroup.h | 1 -
> mm/memcontrol.c | 34 ++++++++++++----------------------
> 2 files changed, 12 insertions(+), 23 deletions(-)
>
> diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
> index 5c831f1eca79..da62ee2be28b 100644
> --- a/include/linux/page_cgroup.h
> +++ b/include/linux/page_cgroup.h
> @@ -5,7 +5,6 @@ enum {
> /* flags for mem_cgroup */
> PCG_USED = 0x01, /* This page is charged to a memcg */
> PCG_MEM = 0x02, /* This page holds a memory charge */
> - PCG_MEMSW = 0x04, /* This page holds a memory+swap charge */
> };
>
> struct pglist_data;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 7709f17347f3..9bab35fc3e9e 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2606,7 +2606,7 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg,
> * have the page locked
> */
> pc->mem_cgroup = memcg;
> - pc->flags = PCG_USED | PCG_MEM | (do_swap_account ? PCG_MEMSW : 0);
> + pc->flags = PCG_USED | PCG_MEM;
>
> if (lrucare)
> unlock_page_lru(page, isolated);
> @@ -5815,7 +5815,6 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
> if (!PageCgroupUsed(pc))
> return;
>
> - VM_BUG_ON_PAGE(!(pc->flags & PCG_MEMSW), page);
> memcg = pc->mem_cgroup;
>
> oldid = swap_cgroup_record(entry, mem_cgroup_id(memcg));
> @@ -6010,17 +6009,16 @@ void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg)
> }
>
> static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
> - unsigned long nr_mem, unsigned long nr_memsw,
> unsigned long nr_anon, unsigned long nr_file,
> unsigned long nr_huge, struct page *dummy_page)
> {
> + unsigned long nr_pages = nr_anon + nr_file;
> unsigned long flags;
>
> if (!mem_cgroup_is_root(memcg)) {
> - if (nr_mem)
> - page_counter_uncharge(&memcg->memory, nr_mem);
> - if (nr_memsw)
> - page_counter_uncharge(&memcg->memsw, nr_memsw);
> + page_counter_uncharge(&memcg->memory, nr_pages);
> + if (do_swap_account)
> + page_counter_uncharge(&memcg->memsw, nr_pages);
> memcg_oom_recover(memcg);
> }
>
> @@ -6029,23 +6027,21 @@ static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
> __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_CACHE], nr_file);
> __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE], nr_huge);
> __this_cpu_add(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT], pgpgout);
> - __this_cpu_add(memcg->stat->nr_page_events, nr_anon + nr_file);
> + __this_cpu_add(memcg->stat->nr_page_events, nr_pages);
> memcg_check_events(memcg, dummy_page);
> local_irq_restore(flags);
>
> if (!mem_cgroup_is_root(memcg))
> - css_put_many(&memcg->css, max(nr_mem, nr_memsw));
> + css_put_many(&memcg->css, nr_pages);
> }
>
> static void uncharge_list(struct list_head *page_list)
> {
> struct mem_cgroup *memcg = NULL;
> - unsigned long nr_memsw = 0;
> unsigned long nr_anon = 0;
> unsigned long nr_file = 0;
> unsigned long nr_huge = 0;
> unsigned long pgpgout = 0;
> - unsigned long nr_mem = 0;
> struct list_head *next;
> struct page *page;
>
> @@ -6072,10 +6068,9 @@ static void uncharge_list(struct list_head *page_list)
>
> if (memcg != pc->mem_cgroup) {
> if (memcg) {
> - uncharge_batch(memcg, pgpgout, nr_mem, nr_memsw,
> - nr_anon, nr_file, nr_huge, page);
> - pgpgout = nr_mem = nr_memsw = 0;
> - nr_anon = nr_file = nr_huge = 0;
> + uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
> + nr_huge, page);
> + pgpgout = nr_anon = nr_file = nr_huge = 0;
> }
> memcg = pc->mem_cgroup;
> }
> @@ -6091,18 +6086,14 @@ static void uncharge_list(struct list_head *page_list)
> else
> nr_file += nr_pages;
>
> - if (pc->flags & PCG_MEM)
> - nr_mem += nr_pages;
> - if (pc->flags & PCG_MEMSW)
> - nr_memsw += nr_pages;
> pc->flags = 0;
>
> pgpgout++;
> } while (next != page_list);
>
> if (memcg)
> - uncharge_batch(memcg, pgpgout, nr_mem, nr_memsw,
> - nr_anon, nr_file, nr_huge, page);
> + uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
> + nr_huge, page);
> }
>
> /**
> @@ -6187,7 +6178,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
> return;
>
> VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM), oldpage);
> - VM_BUG_ON_PAGE(do_swap_account && !(pc->flags & PCG_MEMSW), oldpage);
>
> if (lrucare)
> lock_page_lru(oldpage, &isolated);
> --
> 2.1.2
>
--
Michal Hocko
SUSE Labs
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