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Message-Id: <20210722182627.2267368-1-shakeelb@google.com>
Date: Thu, 22 Jul 2021 11:26:27 -0700
From: Shakeel Butt <shakeelb@...gle.com>
To: Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
Jan Kara <jack@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>, cgroups@...r.kernel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH] writeback: memcg: simplify cgroup_writeback_by_id
Currently cgroup_writeback_by_id calls mem_cgroup_wb_stats() to get
dirty pages for a memcg. However mem_cgroup_wb_stats() does a lot more
than just get the number of dirty pages. Just directly get the number of
dirty pages instead of calling mem_cgroup_wb_stats(). Also
cgroup_writeback_by_id() is only called for best-effort dirty flushing,
so remove the unused 'nr' parameter and no need to explicitly flush
memcg stats.
Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
fs/fs-writeback.c | 20 +++++++++-----------
include/linux/memcontrol.h | 15 +++++++++++++++
include/linux/writeback.h | 2 +-
mm/memcontrol.c | 13 +------------
4 files changed, 26 insertions(+), 24 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 867984e778c3..35894a2dba75 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1039,20 +1039,20 @@ static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
* cgroup_writeback_by_id - initiate cgroup writeback from bdi and memcg IDs
* @bdi_id: target bdi id
* @memcg_id: target memcg css id
- * @nr: number of pages to write, 0 for best-effort dirty flushing
* @reason: reason why some writeback work initiated
* @done: target wb_completion
*
* Initiate flush of the bdi_writeback identified by @bdi_id and @memcg_id
* with the specified parameters.
*/
-int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
+int cgroup_writeback_by_id(u64 bdi_id, int memcg_id,
enum wb_reason reason, struct wb_completion *done)
{
struct backing_dev_info *bdi;
struct cgroup_subsys_state *memcg_css;
struct bdi_writeback *wb;
struct wb_writeback_work *work;
+ unsigned long dirty;
int ret;
/* lookup bdi and memcg */
@@ -1081,24 +1081,22 @@ int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr,
}
/*
- * If @nr is zero, the caller is attempting to write out most of
+ * The caller is attempting to write out most of
* the currently dirty pages. Let's take the current dirty page
* count and inflate it by 25% which should be large enough to
* flush out most dirty pages while avoiding getting livelocked by
* concurrent dirtiers.
+ *
+ * BTW the memcg stats are flushed periodically and this is best-effort
+ * estimation, so some potential error is ok.
*/
- if (!nr) {
- unsigned long filepages, headroom, dirty, writeback;
-
- mem_cgroup_wb_stats(wb, &filepages, &headroom, &dirty,
- &writeback);
- nr = dirty * 10 / 8;
- }
+ dirty = memcg_page_state(mem_cgroup_from_css(memcg_css), NR_FILE_DIRTY);
+ dirty = dirty * 10 / 8;
/* issue the writeback work */
work = kzalloc(sizeof(*work), GFP_NOWAIT | __GFP_NOWARN);
if (work) {
- work->nr_pages = nr;
+ work->nr_pages = dirty;
work->sync_mode = WB_SYNC_NONE;
work->range_cyclic = 1;
work->reason = reason;
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index b4c6b613e162..7028d8e4a3d7 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -989,6 +989,16 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg,
local_irq_restore(flags);
}
+static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
+{
+ long x = READ_ONCE(memcg->vmstats.state[idx]);
+#ifdef CONFIG_SMP
+ if (x < 0)
+ x = 0;
+#endif
+ return x;
+}
+
static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
enum node_stat_item idx)
{
@@ -1444,6 +1454,11 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg,
{
}
+static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
+{
+ return 0;
+}
+
static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
enum node_stat_item idx)
{
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 1f34ddf284dc..109e0dcd1d21 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -218,7 +218,7 @@ void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
void wbc_detach_inode(struct writeback_control *wbc);
void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
size_t bytes);
-int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, unsigned long nr_pages,
+int cgroup_writeback_by_id(u64 bdi_id, int memcg_id,
enum wb_reason reason, struct wb_completion *done);
void cgroup_writeback_umount(void);
bool cleanup_offline_cgwb(struct bdi_writeback *wb);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 35bb5f8f9ea8..6580c2381a3e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -631,17 +631,6 @@ void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val)
cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id());
}
-/* idx can be of type enum memcg_stat_item or node_stat_item. */
-static unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
-{
- long x = READ_ONCE(memcg->vmstats.state[idx]);
-#ifdef CONFIG_SMP
- if (x < 0)
- x = 0;
-#endif
- return x;
-}
-
/* idx can be of type enum memcg_stat_item or node_stat_item. */
static unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx)
{
@@ -4609,7 +4598,7 @@ void mem_cgroup_flush_foreign(struct bdi_writeback *wb)
atomic_read(&frn->done.cnt) == 1) {
frn->at = 0;
trace_flush_foreign(wb, frn->bdi_id, frn->memcg_id);
- cgroup_writeback_by_id(frn->bdi_id, frn->memcg_id, 0,
+ cgroup_writeback_by_id(frn->bdi_id, frn->memcg_id,
WB_REASON_FOREIGN_FLUSH,
&frn->done);
}
--
2.32.0.432.gabb21c7263-goog
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