Commit 3ea67d06 authored by Sha Zhengju's avatar Sha Zhengju Committed by Linus Torvalds

memcg: add per cgroup writeback pages accounting

Add memcg routines to count writeback pages, later dirty pages will also
be accounted.

After Kame's commit 89c06bd5 ("memcg: use new logic for page stat
accounting"), we can use 'struct page' flag to test page state instead
of per page_cgroup flag.  But memcg has a feature to move a page from a
cgroup to another one and may have race between "move" and "page stat
accounting".  So in order to avoid the race we have designed a new lock:

         mem_cgroup_begin_update_page_stat()
         modify page information        -->(a)
         mem_cgroup_update_page_stat()  -->(b)
         mem_cgroup_end_update_page_stat()

It requires both (a) and (b)(writeback pages accounting) to be pretected
in mem_cgroup_{begin/end}_update_page_stat().  It's full no-op for
!CONFIG_MEMCG, almost no-op if memcg is disabled (but compiled in), rcu
read lock in the most cases (no task is moving), and spin_lock_irqsave
on top in the slow path.

There're two writeback interfaces to modify: test_{clear/set}_page_writeback().
And the lock order is:
	--> memcg->move_lock
	  --> mapping->tree_lock
Signed-off-by: default avatarSha Zhengju <handai.szj@taobao.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Reviewed-by: default avatarGreg Thelen <gthelen@google.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 658b72c5
......@@ -42,6 +42,7 @@ enum mem_cgroup_stat_index {
MEM_CGROUP_STAT_RSS, /* # of pages charged as anon rss */
MEM_CGROUP_STAT_RSS_HUGE, /* # of pages charged as anon huge */
MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
MEM_CGROUP_STAT_WRITEBACK, /* # of pages under writeback */
MEM_CGROUP_STAT_SWAP, /* # of pages, swapped out */
MEM_CGROUP_STAT_NSTATS,
};
......
......@@ -89,6 +89,7 @@ static const char * const mem_cgroup_stat_names[] = {
"rss",
"rss_huge",
"mapped_file",
"writeback",
"swap",
};
......@@ -3654,6 +3655,20 @@ void mem_cgroup_split_huge_fixup(struct page *head)
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
static inline
void mem_cgroup_move_account_page_stat(struct mem_cgroup *from,
struct mem_cgroup *to,
unsigned int nr_pages,
enum mem_cgroup_stat_index idx)
{
/* Update stat data for mem_cgroup */
preempt_disable();
WARN_ON_ONCE(from->stat->count[idx] < nr_pages);
__this_cpu_add(from->stat->count[idx], -nr_pages);
__this_cpu_add(to->stat->count[idx], nr_pages);
preempt_enable();
}
/**
* mem_cgroup_move_account - move account of the page
* @page: the page
......@@ -3699,13 +3714,14 @@ static int mem_cgroup_move_account(struct page *page,
move_lock_mem_cgroup(from, &flags);
if (!anon && page_mapped(page)) {
/* Update mapped_file data for mem_cgroup */
preempt_disable();
__this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
__this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
preempt_enable();
}
if (!anon && page_mapped(page))
mem_cgroup_move_account_page_stat(from, to, nr_pages,
MEM_CGROUP_STAT_FILE_MAPPED);
if (PageWriteback(page))
mem_cgroup_move_account_page_stat(from, to, nr_pages,
MEM_CGROUP_STAT_WRITEBACK);
mem_cgroup_charge_statistics(from, page, anon, -nr_pages);
/* caller should have done css_get */
......
......@@ -2143,11 +2143,17 @@ EXPORT_SYMBOL(account_page_dirtied);
/*
* Helper function for set_page_writeback family.
*
* The caller must hold mem_cgroup_begin/end_update_page_stat() lock
* while calling this function.
* See test_set_page_writeback for example.
*
* NOTE: Unlike account_page_dirtied this does not rely on being atomic
* wrt interrupts.
*/
void account_page_writeback(struct page *page)
{
mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
inc_zone_page_state(page, NR_WRITEBACK);
}
EXPORT_SYMBOL(account_page_writeback);
......@@ -2364,7 +2370,10 @@ int test_clear_page_writeback(struct page *page)
{
struct address_space *mapping = page_mapping(page);
int ret;
bool locked;
unsigned long memcg_flags;
mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags);
if (mapping) {
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
......@@ -2385,9 +2394,11 @@ int test_clear_page_writeback(struct page *page)
ret = TestClearPageWriteback(page);
}
if (ret) {
mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
dec_zone_page_state(page, NR_WRITEBACK);
inc_zone_page_state(page, NR_WRITTEN);
}
mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags);
return ret;
}
......@@ -2395,7 +2406,10 @@ int test_set_page_writeback(struct page *page)
{
struct address_space *mapping = page_mapping(page);
int ret;
bool locked;
unsigned long memcg_flags;
mem_cgroup_begin_update_page_stat(page, &locked, &memcg_flags);
if (mapping) {
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
......@@ -2422,6 +2436,7 @@ int test_set_page_writeback(struct page *page)
}
if (!ret)
account_page_writeback(page);
mem_cgroup_end_update_page_stat(page, &locked, &memcg_flags);
return ret;
}
......
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