[PATCH 3/3] writeback: specify writeback period and expire interval per memcg

From: Xie Yongmei
Date: Wed Apr 27 2022 - 05:37:28 EST

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dirty_writeback_interval: dirty wakeup period
dirty_expire_interval: expire period

This patch provides per memcg setttings for writeback interval.

Dirty writeback could be triggered in the below ways:
- mark_inode_dirty: when the first time of dirtying pages for this inode,
it tries to wakeup the callback hook wb_workfn in
wakeup period later.
- wb_workfn: if there're more writeback works to do, it would wakeup the
callback hook wb_workfn in another wakeup period later.
- external event: kswad found dirty pages piled up at the end of inactive
list or desktop mode timer.
- buffered write context: balance_dirty_pages tries to wake up background
writeback once dirty pages above freerun level of pages.
- sync context: sync(fs sync) writeback immediately

No matter how writeback is triggered, wb_workfn is the unique callback hook
to manipulate the flushing things. Actually, wb_check_old_data_flush
handles the period writeback and decides the scope of dirty pages which
have to be written back because they were too old.

Signed-off-by: Xie Yongmei <yongmeixie@xxxxxxxxxxx>
---
fs/fs-writeback.c | 11 ++--
include/linux/memcontrol.h | 16 ++++++
mm/backing-dev.c | 4 +-
mm/memcontrol.c | 114 +++++++++++++++++++++++++++++++++++++
4 files changed, 140 insertions(+), 5 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 591fe9cf1659..f59e4709ec39 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1980,6 +1980,7 @@ static long wb_writeback(struct bdi_writeback *wb,
struct inode *inode;
long progress;
struct blk_plug plug;
+ unsigned int dirty_expire = wb_dirty_expire_interval(wb);

blk_start_plug(&plug);
spin_lock(&wb->list_lock);
@@ -2015,7 +2016,7 @@ static long wb_writeback(struct bdi_writeback *wb,
*/
if (work->for_kupdate) {
dirtied_before = jiffies -
- msecs_to_jiffies(dirty_expire_interval * 10);
+ msecs_to_jiffies(dirty_expire * 10);
} else if (work->for_background)
dirtied_before = jiffies;

@@ -2101,15 +2102,16 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
{
unsigned long expired;
long nr_pages;
+ unsigned int writeback_interval = wb_dirty_writeback_interval(wb);

/*
* When set to zero, disable periodic writeback
*/
- if (!dirty_writeback_interval)
+ if (!writeback_interval)
return 0;

expired = wb->last_old_flush +
- msecs_to_jiffies(dirty_writeback_interval * 10);
+ msecs_to_jiffies(writeback_interval * 10);
if (time_before(jiffies, expired))
return 0;

@@ -2194,6 +2196,7 @@ void wb_workfn(struct work_struct *work)
struct bdi_writeback *wb = container_of(to_delayed_work(work),
struct bdi_writeback, dwork);
long pages_written;
+ unsigned int writeback_interval = wb_dirty_writeback_interval(wb);

set_worker_desc("flush-%s", bdi_dev_name(wb->bdi));

@@ -2222,7 +2225,7 @@ void wb_workfn(struct work_struct *work)

if (!list_empty(&wb->work_list))
wb_wakeup(wb);
- else if (wb_has_dirty_io(wb) && dirty_writeback_interval)
+ else if (wb_has_dirty_io(wb) && writeback_interval)
wb_wakeup_delayed(wb);
}

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 386fc9b70c95..c1dc88bb8f80 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -347,6 +347,8 @@ struct mem_cgroup {
#ifdef CONFIG_CGROUP_WRITEBACK_PARA
int dirty_background_ratio;
int dirty_ratio;
+ int dirty_writeback_interval;
+ int dirty_expire_interval;
#endif

struct mem_cgroup_per_node *nodeinfo[];
@@ -1642,6 +1644,8 @@ static inline void mem_cgroup_flush_foreign(struct bdi_writeback *wb)
#ifdef CONFIG_CGROUP_WRITEBACK_PARA
unsigned int wb_dirty_background_ratio(struct bdi_writeback *wb);
unsigned int wb_dirty_ratio(struct bdi_writeback *wb);
+unsigned int wb_dirty_writeback_interval(struct bdi_writeback *wb);
+unsigned int wb_dirty_expire_interval(struct bdi_writeback *wb);
#else
static inline
unsigned int wb_dirty_background_ratio(struct bdi_writeback *wb)
@@ -1654,6 +1658,18 @@ unsigned int wb_dirty_ratio(struct bdi_writeback *wb)
{
return vm_dirty_ratio;
}
+
+static inline
+unsigned int wb_dirty_writeback_interval(struct bdi_writeback *wb)
+{
+ return dirty_writeback_interval;
+}
+
+static inline
+unsigned int wb_dirty_expire_interval(struct bdi_writeback *wb)
+{
+ return dirty_expire_interval;
+}
#endif

struct sock;
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7176af65b103..685558362ad8 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -15,6 +15,7 @@
#include <linux/writeback.h>
#include <linux/device.h>
#include <trace/events/writeback.h>
+#include <linux/memcontrol.h>

struct backing_dev_info noop_backing_dev_info;
EXPORT_SYMBOL_GPL(noop_backing_dev_info);
@@ -264,8 +265,9 @@ subsys_initcall(default_bdi_init);
void wb_wakeup_delayed(struct bdi_writeback *wb)
{
unsigned long timeout;
+ unsigned int dirty_interval = wb_dirty_writeback_interval(wb);

- timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
+ timeout = msecs_to_jiffies(dirty_interval * 10);
spin_lock_bh(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
queue_delayed_work(bdi_wq, &wb->dwork, timeout);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b1c1b150637a..c392aec22e2e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4851,17 +4851,49 @@ unsigned int wb_dirty_ratio(struct bdi_writeback *wb)
return memcg->dirty_ratio;
}

+unsigned int wb_dirty_writeback_interval(struct bdi_writeback *wb)
+{
+ struct mem_cgroup *memcg;
+
+ if (mem_cgroup_disabled() || !wb)
+ return dirty_writeback_interval;
+
+ memcg = mem_cgroup_from_css(wb->memcg_css);
+ if (memcg == root_mem_cgroup || memcg->dirty_writeback_interval < 0)
+ return dirty_writeback_interval;
+
+ return memcg->dirty_writeback_interval;
+}
+
+unsigned int wb_dirty_expire_interval(struct bdi_writeback *wb)
+{
+ struct mem_cgroup *memcg;
+
+ if (mem_cgroup_disabled() || !wb)
+ return dirty_expire_interval;
+
+ memcg = mem_cgroup_from_css(wb->memcg_css);
+ if (memcg == root_mem_cgroup || memcg->dirty_expire_interval < 0)
+ return dirty_expire_interval;
+
+ return memcg->dirty_expire_interval;
+}
+
static void wb_memcg_inherit_from_parent(struct mem_cgroup *parent,
struct mem_cgroup *memcg)
{
memcg->dirty_background_ratio = parent->dirty_background_ratio;
memcg->dirty_ratio = parent->dirty_ratio;
+ memcg->dirty_writeback_interval = parent->dirty_writeback_interval;
+ memcg->dirty_expire_interval = parent->dirty_expire_interval;
}

static void wb_memcg_init(struct mem_cgroup *memcg)
{
memcg->dirty_background_ratio = -1;
memcg->dirty_ratio = -1;
+ memcg->dirty_writeback_interval = -1;
+ memcg->dirty_expire_interval = -1;
}

static int mem_cgroup_dirty_background_ratio_show(struct seq_file *m, void *v)
@@ -4918,6 +4950,64 @@ mem_cgroup_dirty_ratio_write(struct kernfs_open_file *of,
memcg->dirty_ratio = dirty_ratio;
return nbytes;
}
+
+static int mem_cgroup_dirty_writeback_interval_show(struct seq_file *m, void *v)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
+
+ seq_printf(m, "%d\n", memcg->dirty_writeback_interval);
+ return 0;
+}
+
+static ssize_t
+mem_cgroup_dirty_writeback_interval_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+ int ret, writeback_interval;
+
+ buf = strstrip(buf);
+ ret = kstrtoint(buf, 0, &writeback_interval);
+ if (ret)
+ return ret;
+
+ if (writeback_interval < -1)
+ return -EINVAL;
+
+ if (memcg->dirty_writeback_interval != writeback_interval) {
+ memcg->dirty_writeback_interval = writeback_interval;
+ wakeup_flusher_threads(WB_REASON_PERIODIC);
+ }
+ return nbytes;
+}
+
+static int mem_cgroup_dirty_expire_interval_show(struct seq_file *m, void *v)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
+
+ seq_printf(m, "%d\n", memcg->dirty_expire_interval);
+ return 0;
+}
+
+static ssize_t
+mem_cgroup_dirty_expire_interval_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
+ int ret, expire_interval;
+
+ buf = strstrip(buf);
+ ret = kstrtoint(buf, 0, &expire_interval);
+ if (ret)
+ return ret;
+
+ if (expire_interval < -1)
+ return -EINVAL;
+
+ memcg->dirty_expire_interval = expire_interval;
+ return nbytes;
+}
#else
static void wb_memcg_inherit_from_parent(struct mem_cgroup *parent,
struct mem_cgroup *memcg)
@@ -5067,6 +5157,18 @@ static struct cftype mem_cgroup_legacy_files[] = {
.seq_show = mem_cgroup_dirty_ratio_show,
.write = mem_cgroup_dirty_ratio_write,
},
+ {
+ .name = "dirty_writeback_interval_centisecs",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = mem_cgroup_dirty_writeback_interval_show,
+ .write = mem_cgroup_dirty_writeback_interval_write,
+ },
+ {
+ .name = "dirty_expire_interval_centisecs",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = mem_cgroup_dirty_expire_interval_show,
+ .write = mem_cgroup_dirty_expire_interval_write,
+ },
#endif
{ }, /* terminate */
};
@@ -6549,6 +6651,18 @@ static struct cftype memory_files[] = {
.seq_show = mem_cgroup_dirty_ratio_show,
.write = mem_cgroup_dirty_ratio_write,
},
+ {
+ .name = "dirty_writeback_interval_centisecs",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = mem_cgroup_dirty_writeback_interval_show,
+ .write = mem_cgroup_dirty_writeback_interval_write,
+ },
+ {
+ .name = "dirty_expire_interval_centisecs",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = mem_cgroup_dirty_expire_interval_show,
+ .write = mem_cgroup_dirty_expire_interval_write,
+ },
#endif
{ } /* terminate */
};
--
2.27.0

Next message: Tao Zhou: "Re: [PATCH v6 2/7] sched/fair: Decay task PELT values during wakeup migration"
Previous message: Greg KH: "Re: [PATCH v4] arch_topology: Trace the update thermal pressure"
Next in thread: Michal Hocko: "Re: [PATCH 3/3] writeback: specify writeback period and expire interval per memcg"
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