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Subject[PATCH V2 5/6] memcg: add per cgroup writeback pages accounting
Date
From: Sha Zhengju <handai.szj@taobao.com>

Similar to dirty page, we add per cgroup writeback pages accounting. The lock
rule still is:
mem_cgroup_begin_update_page_stat()
modify page WRITEBACK stat
mem_cgroup_update_page_stat()
mem_cgroup_end_update_page_stat()

There're two writeback interface to modify: test_clear/set_page_writeback.

Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
---
include/linux/memcontrol.h | 1 +
mm/memcontrol.c | 5 +++++
mm/page-writeback.c | 17 +++++++++++++++++
3 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 8c6b8ca..0c8a699 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -42,6 +42,7 @@ enum mem_cgroup_stat_index {
MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
MEM_CGROUP_STAT_SWAP, /* # of pages, swapped out */
MEM_CGROUP_STAT_FILE_DIRTY, /* # of dirty pages in page cache */
+ MEM_CGROUP_STAT_WRITEBACK, /* # of pages under writeback */
MEM_CGROUP_STAT_NSTATS,
};

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index cdcd547..de91d3d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -86,6 +86,7 @@ static const char * const mem_cgroup_stat_names[] = {
"mapped_file",
"swap",
"dirty",
+ "writeback",
};

enum mem_cgroup_events_index {
@@ -2607,6 +2608,10 @@ static int mem_cgroup_move_account(struct page *page,
mem_cgroup_move_account_page_stat(from, to,
MEM_CGROUP_STAT_FILE_DIRTY);

+ if (PageWriteback(page))
+ mem_cgroup_move_account_page_stat(from, to,
+ MEM_CGROUP_STAT_WRITEBACK);
+
mem_cgroup_charge_statistics(from, anon, -nr_pages);

/* caller should have done css_get */
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 233e7ac..6b06d5e 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1956,11 +1956,17 @@ 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 modifying struct page state and accounting writeback pages.
+ * 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);
@@ -2192,7 +2198,10 @@ int test_clear_page_writeback(struct page *page)
{
struct address_space *mapping = page_mapping(page);
int ret;
+ bool locked;
+ unsigned long flags;

+ mem_cgroup_begin_update_page_stat(page, &locked, &flags);
if (mapping) {
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
@@ -2213,9 +2222,12 @@ 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, &flags);
return ret;
}

@@ -2223,7 +2235,10 @@ int test_set_page_writeback(struct page *page)
{
struct address_space *mapping = page_mapping(page);
int ret;
+ bool locked;
+ unsigned long flags;

+ mem_cgroup_begin_update_page_stat(page, &locked, &flags);
if (mapping) {
struct backing_dev_info *bdi = mapping->backing_dev_info;
unsigned long flags;
@@ -2250,6 +2265,8 @@ int test_set_page_writeback(struct page *page)
}
if (!ret)
account_page_writeback(page);
+
+ mem_cgroup_end_update_page_stat(page, &locked, &flags);
return ret;

}
--
1.7.1


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