From: Sha Zhengju <handai.szj@xxxxxxxxxx>
This patch is to 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: Sha Zhengju <handai.szj@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Reviewed-by: Greg Thelen <gthelen@xxxxxxxxxx>
---
include/linux/memcontrol.h | 1 +
mm/memcontrol.c | 30 +++++++++++++++++++++++-------
mm/page-writeback.c | 15 +++++++++++++++
3 files changed, 39 insertions(+), 7 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 630bfa1..1878644 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -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,
};
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0a50871..869bfaf 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -89,6 +89,7 @@ static const char * const mem_cgroup_stat_names[] = {
"rss",
"rss_huge",
"mapped_file",
+ "writeback",
"swap",
};
@@ -3675,6 +3676,20 @@ 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
@@ -3720,13 +3735,14 @@ 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 */
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index ddc56fc..b6ecbc6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1999,11 +1999,17 @@ 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);
@@ -2220,7 +2226,10 @@ 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;
@@ -2241,9 +2250,11 @@ 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;
}
@@ -2251,7 +2262,10 @@ 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;
@@ -2278,6 +2292,7 @@ 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;
}
--
1.7.9.5
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