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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.

Link: https://lkml.kernel.org/r/20210722182627.2267368-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Shakeel Butt 2021-09-02 14:53:27 -07:00 committed by Linus Torvalds
parent 7ae12c809f
commit 7490a2d248
4 changed files with 26 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
fs/fs-writeback.c
View File

@ -1039,20 +1039,20 @@ restart:
* 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;

15
include/linux/memcontrol.h
View File

@ -955,6 +955,16 @@ 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)
{
@ -1391,6 +1401,11 @@ 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)
{

2
include/linux/writeback.h
View File

@ -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);

13
mm/memcontrol.c
View File

@ -645,17 +645,6 @@ 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)
{
@ -4668,7 +4657,7 @@ 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);
}