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Date: Wed, 27 Apr 2022 12:36:43 +0200
From: Michal Hocko <mhocko@...e.com>
To: Xie Yongmei <yongmeixie@...mail.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-fsdevel@...r.kernel.org, yongmeixie@...mail.com,
Johannes Weiner <hannes@...xchg.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Shakeel Butt <shakeelb@...gle.com>, Tejun Heo <tj@...nel.org>,
linux-api@...r.kernel.org
Subject: Re: [PATCH 3/3] writeback: specify writeback period and expire
interval per memcg
[updated CC list as per previous patch in the thread]
On Wed 27-04-22 05:32:41, Xie Yongmei wrote:
> 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@...mail.com>
> ---
> 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
--
Michal Hocko
SUSE Labs
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