Re: [PATCH 11/14] mm: memcontrol: do not account memory+swap on unified hierarchy

Michal Hocko
2015-11-13T10:37:57Z

On Thu 12-11-15 18:41:30, Johannes Weiner wrote:
> The unified hierarchy memory controller doesn't expose the memory+swap
> counter to userspace, but its accounting is hardcoded in all charge
> paths right now, including the per-cpu charge cache ("the stock").
>
> To avoid adding yet more pointless memory+swap accounting with the
> socket memory support in unified hierarchy, disable the counter
> altogether when in unified hierarchy mode.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/memcontrol.c | 44 +++++++++++++++++++++++++-------------------
> 1 file changed, 25 insertions(+), 19 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 658bef2..e7f1a79 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -87,6 +87,12 @@ int do_swap_account __read_mostly;
> #define do_swap_account 0
> #endif
>
> +/* Whether legacy memory+swap accounting is active */
> +static bool do_memsw_account(void)
> +{
> + return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && do_swap_account;
> +}
> +
> static const char * const mem_cgroup_stat_names[] = {
> "cache",
> "rss",
> @@ -1177,7 +1183,7 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
> if (count < limit)
> margin = limit - count;
>
> - if (do_swap_account) {
> + if (do_memsw_account()) {
> count = page_counter_read(&memcg->memsw);
> limit = READ_ONCE(memcg->memsw.limit);
> if (count <= limit)
> @@ -1280,7 +1286,7 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> pr_cont(":");
>
> for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
> - if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
> + if (i == MEM_CGROUP_STAT_SWAP && !do_memsw_account())
> continue;
> pr_cont(" %s:%luKB", mem_cgroup_stat_names[i],
> K(mem_cgroup_read_stat(iter, i)));
> @@ -1903,7 +1909,7 @@ static void drain_stock(struct memcg_stock_pcp *stock)
>
> if (stock->nr_pages) {
> page_counter_uncharge(&old->memory, stock->nr_pages);
> - if (do_swap_account)
> + if (do_memsw_account())
> page_counter_uncharge(&old->memsw, stock->nr_pages);
> css_put_many(&old->css, stock->nr_pages);
> stock->nr_pages = 0;
> @@ -2033,11 +2039,11 @@ retry:
> if (consume_stock(memcg, nr_pages))
> return 0;
>
> - if (!do_swap_account ||
> + if (!do_memsw_account() ||
> page_counter_try_charge(&memcg->memsw, batch, &counter)) {
> if (page_counter_try_charge(&memcg->memory, batch, &counter))
> goto done_restock;
> - if (do_swap_account)
> + if (do_memsw_account())
> page_counter_uncharge(&memcg->memsw, batch);
> mem_over_limit = mem_cgroup_from_counter(counter, memory);
> } else {
> @@ -2124,7 +2130,7 @@ force:
> * temporarily by force charging it.
> */
> page_counter_charge(&memcg->memory, nr_pages);
> - if (do_swap_account)
> + if (do_memsw_account())
> page_counter_charge(&memcg->memsw, nr_pages);
> css_get_many(&memcg->css, nr_pages);
>
> @@ -2161,7 +2167,7 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages)
> return;
>
> page_counter_uncharge(&memcg->memory, nr_pages);
> - if (do_swap_account)
> + if (do_memsw_account())
> page_counter_uncharge(&memcg->memsw, nr_pages);
>
> css_put_many(&memcg->css, nr_pages);
> @@ -2441,7 +2447,7 @@ void __memcg_kmem_uncharge(struct page *page, int order)
>
> page_counter_uncharge(&memcg->kmem, nr_pages);
> page_counter_uncharge(&memcg->memory, nr_pages);
> - if (do_swap_account)
> + if (do_memsw_account())
> page_counter_uncharge(&memcg->memsw, nr_pages);
>
> page->mem_cgroup = NULL;
> @@ -3154,7 +3160,7 @@ static int memcg_stat_show(struct seq_file *m, void *v)
> BUILD_BUG_ON(ARRAY_SIZE(mem_cgroup_lru_names) != NR_LRU_LISTS);
>
> for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
> - if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
> + if (i == MEM_CGROUP_STAT_SWAP && !do_memsw_account())
> continue;
> seq_printf(m, "%s %lu\n", mem_cgroup_stat_names[i],
> mem_cgroup_read_stat(memcg, i) * PAGE_SIZE);
> @@ -3176,14 +3182,14 @@ static int memcg_stat_show(struct seq_file *m, void *v)
> }
> seq_printf(m, "hierarchical_memory_limit %llu\n",
> (u64)memory * PAGE_SIZE);
> - if (do_swap_account)
> + if (do_memsw_account())
> seq_printf(m, "hierarchical_memsw_limit %llu\n",
> (u64)memsw * PAGE_SIZE);
>
> for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
> unsigned long long val = 0;
>
> - if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
> + if (i == MEM_CGROUP_STAT_SWAP && !do_memsw_account())
> continue;
> for_each_mem_cgroup_tree(mi, memcg)
> val += mem_cgroup_read_stat(mi, i) * PAGE_SIZE;
> @@ -3314,7 +3320,7 @@ static void mem_cgroup_threshold(struct mem_cgroup *memcg)
> {
> while (memcg) {
> __mem_cgroup_threshold(memcg, false);
> - if (do_swap_account)
> + if (do_memsw_account())
> __mem_cgroup_threshold(memcg, true);
>
> memcg = parent_mem_cgroup(memcg);
> @@ -4460,7 +4466,7 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
> * we call find_get_page() with swapper_space directly.
> */
> page = find_get_page(swap_address_space(ent), ent.val);
> - if (do_swap_account)
> + if (do_memsw_account())
> entry->val = ent.val;
>
> return page;
> @@ -4495,7 +4501,7 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
> page = find_get_entry(mapping, pgoff);
> if (radix_tree_exceptional_entry(page)) {
> swp_entry_t swp = radix_to_swp_entry(page);
> - if (do_swap_account)
> + if (do_memsw_account())
> *entry = swp;
> page = find_get_page(swap_address_space(swp), swp.val);
> }
> @@ -5270,7 +5276,7 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm,
> if (page->mem_cgroup)
> goto out;
>
> - if (do_swap_account) {
> + if (do_memsw_account()) {
> swp_entry_t ent = { .val = page_private(page), };
> unsigned short id = lookup_swap_cgroup_id(ent);
>
> @@ -5334,7 +5340,7 @@ void mem_cgroup_commit_charge(struct page *page, struct mem_cgroup *memcg,
> memcg_check_events(memcg, page);
> local_irq_enable();
>
> - if (do_swap_account && PageSwapCache(page)) {
> + if (do_memsw_account() && PageSwapCache(page)) {
> swp_entry_t entry = { .val = page_private(page) };
> /*
> * The swap entry might not get freed for a long time,
> @@ -5379,7 +5385,7 @@ static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
>
> if (!mem_cgroup_is_root(memcg)) {
> page_counter_uncharge(&memcg->memory, nr_pages);
> - if (do_swap_account)
> + if (do_memsw_account())
> page_counter_uncharge(&memcg->memsw, nr_pages);
> memcg_oom_recover(memcg);
> }
> @@ -5587,7 +5593,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
> VM_BUG_ON_PAGE(PageLRU(page), page);
> VM_BUG_ON_PAGE(page_count(page), page);
>
> - if (!do_swap_account)
> + if (!do_memsw_account())
> return;
>
> memcg = page->mem_cgroup;
> @@ -5627,7 +5633,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry)
> struct mem_cgroup *memcg;
> unsigned short id;
>
> - if (!do_swap_account)
> + if (!do_memsw_account())
> return;
>
> id = swap_cgroup_record(entry, 0);
> --
> 2.6.2

--
Michal Hocko
SUSE Labs