[PATCH 10/14] mm: memcontrol: do not account memory+swap on unified hierarchy

Johannes Weiner
2015-12-08T15:31:19Z

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>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: David S. Miller <davem@davemloft.net>
---
mm/memcontrol.c | 44 +++++++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0602bee..6b8c0f7 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);
@@ -2447,7 +2453,7 @@ 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;
@@ -3160,7 +3166,7 @@ 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);
@@ -3182,14 +3188,14 @@ 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;
@@ -3320,7 +3326,7 @@ 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);
@@ -4466,7 +4472,7 @@ 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;
@@ -4501,7 +4507,7 @@ 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);
}
@@ -5276,7 +5282,7 @@ 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);

@@ -5340,7 +5346,7 @@ 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,
@@ -5385,7 +5391,7 @@ 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);
}
@@ -5593,7 +5599,7 @@ 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;
@@ -5633,7 +5639,7 @@ 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);
--
2.6.3