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Wysocki" , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , "=?UTF-8?q?Eugenio=20P=C3=A9rez?=" , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Mike Rapoport , Shuah Khan , Christian Brauner , Daniel Watson , Yuanchu Xie , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" For reliable and timely aging on memcgs, one has to read the page age histograms on time. A kernel thread makes it easier by aging memcgs with valid refresh_interval when they can be refreshed, and also reduces the latency of any userspace consumers of the page age histogram. The kerne aging thread is gated behind CONFIG_WORKINGSET_REPORT_AGING. Debugging stats may be added in the future for when aging cannot keep up with the configured refresh_interval. Signed-off-by: Yuanchu Xie --- include/linux/workingset_report.h | 10 ++- mm/Kconfig | 6 ++ mm/Makefile | 1 + mm/memcontrol.c | 2 +- mm/workingset_report.c | 13 ++- mm/workingset_report_aging.c | 127 ++++++++++++++++++++++++++++++ 6 files changed, 154 insertions(+), 5 deletions(-) create mode 100644 mm/workingset_report_aging.c diff --git a/include/linux/workingset_report.h b/include/linux/workingset_r= eport.h index 616be6469768..f6bbde2a04c3 100644 --- a/include/linux/workingset_report.h +++ b/include/linux/workingset_report.h @@ -64,7 +64,15 @@ void wsr_remove_sysfs(struct node *node); * The next refresh time is stored in refresh_time. */ bool wsr_refresh_report(struct wsr_state *wsr, struct mem_cgroup *root, - struct pglist_data *pgdat); + struct pglist_data *pgdat, unsigned long *refresh_time); + +#ifdef CONFIG_WORKINGSET_REPORT_AGING +void wsr_wakeup_aging_thread(void); +#else /* CONFIG_WORKINGSET_REPORT_AGING */ +static inline void wsr_wakeup_aging_thread(void) +{ +} +#endif /* CONFIG_WORKINGSET_REPORT_AGING */ =20 int wsr_set_refresh_interval(struct wsr_state *wsr, unsigned long refresh_interval); diff --git a/mm/Kconfig b/mm/Kconfig index be949786796d..a8def8c65610 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1310,6 +1310,12 @@ config WORKINGSET_REPORT This option exports stats and events giving the user more insight into its memory working set. =20 +config WORKINGSET_REPORT_AGING + bool "Workingset report kernel aging thread" + depends on WORKINGSET_REPORT + help + Performs aging on memcgs with their configured refresh intervals. + source "mm/damon/Kconfig" =20 endmenu diff --git a/mm/Makefile b/mm/Makefile index f5ef0768253a..3a282510f960 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -99,6 +99,7 @@ obj-$(CONFIG_PAGE_COUNTER) +=3D page_counter.o obj-$(CONFIG_MEMCG_V1) +=3D memcontrol-v1.o obj-$(CONFIG_MEMCG) +=3D memcontrol.o vmpressure.o obj-$(CONFIG_WORKINGSET_REPORT) +=3D workingset_report.o +obj-$(CONFIG_WORKINGSET_REPORT_AGING) +=3D workingset_report_aging.o ifdef CONFIG_SWAP obj-$(CONFIG_MEMCG) +=3D swap_cgroup.o endif diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d1032c6efc66..ea83f10b22a1 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4462,7 +4462,7 @@ static int memory_ws_page_age_show(struct seq_file *m= , void *v) if (!READ_ONCE(wsr->page_age)) continue; =20 - wsr_refresh_report(wsr, memcg, NODE_DATA(nid)); + wsr_refresh_report(wsr, memcg, NODE_DATA(nid), NULL); mutex_lock(&wsr->page_age_lock); if (!wsr->page_age) goto unlock; diff --git a/mm/workingset_report.c b/mm/workingset_report.c index 1e1bdb8bf75b..dad539e602bb 100644 --- a/mm/workingset_report.c +++ b/mm/workingset_report.c @@ -283,7 +283,7 @@ static void copy_node_bins(struct pglist_data *pgdat, } =20 bool wsr_refresh_report(struct wsr_state *wsr, struct mem_cgroup *root, - struct pglist_data *pgdat) + struct pglist_data *pgdat, unsigned long *refresh_time) { struct wsr_page_age_histo *page_age; unsigned long refresh_interval =3D READ_ONCE(wsr->refresh_interval); @@ -300,10 +300,14 @@ bool wsr_refresh_report(struct wsr_state *wsr, struct= mem_cgroup *root, goto unlock; if (page_age->timestamp && time_is_after_jiffies(page_age->timestamp + refresh_interval)) - goto unlock; + goto time; refresh_scan(wsr, root, pgdat, refresh_interval); copy_node_bins(pgdat, page_age); refresh_aggregate(page_age, root, pgdat); + +time: + if (refresh_time) + *refresh_time =3D page_age->timestamp + refresh_interval; unlock: mutex_unlock(&wsr->page_age_lock); return !!page_age; @@ -386,6 +390,9 @@ int wsr_set_refresh_interval(struct wsr_state *wsr, WRITE_ONCE(wsr->refresh_interval, msecs_to_jiffies(refresh_interval)); unlock: mutex_unlock(&wsr->page_age_lock); + if (!err && refresh_interval && + (!old_interval || jiffies_to_msecs(old_interval) > refresh_interval)) + wsr_wakeup_aging_thread(); return err; } =20 @@ -491,7 +498,7 @@ static ssize_t page_age_show(struct kobject *kobj, stru= ct kobj_attribute *attr, int ret =3D 0; struct wsr_state *wsr =3D kobj_to_wsr(kobj); =20 - wsr_refresh_report(wsr, NULL, kobj_to_pgdat(kobj)); + wsr_refresh_report(wsr, NULL, kobj_to_pgdat(kobj), NULL); =20 mutex_lock(&wsr->page_age_lock); if (!wsr->page_age) diff --git a/mm/workingset_report_aging.c b/mm/workingset_report_aging.c new file mode 100644 index 000000000000..91ad5020778a --- /dev/null +++ b/mm/workingset_report_aging.c @@ -0,0 +1,127 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Workingset report kernel aging thread + * + * Performs aging on behalf of memcgs with their configured refresh interv= al. + * While a userspace program can periodically read the page age breakdown + * per-memcg and trigger aging, the kernel performing aging is less overhe= ad, + * more consistent, and more reliable for the use case where every memcg s= hould + * be aged according to their refresh interval. + */ +#define pr_fmt(fmt) "workingset report aging: " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +static DECLARE_WAIT_QUEUE_HEAD(aging_wait); +static bool refresh_pending; + +static bool do_aging_node(int nid, unsigned long *next_wake_time) +{ + struct mem_cgroup *memcg; + bool should_wait =3D true; + struct pglist_data *pgdat =3D NODE_DATA(nid); + + memcg =3D mem_cgroup_iter(NULL, NULL, NULL); + do { + struct lruvec *lruvec =3D mem_cgroup_lruvec(memcg, pgdat); + struct wsr_state *wsr =3D &lruvec->wsr; + unsigned long refresh_time; + + /* use returned time to decide when to wake up next */ + if (wsr_refresh_report(wsr, memcg, pgdat, &refresh_time)) { + if (should_wait) { + should_wait =3D false; + *next_wake_time =3D refresh_time; + } else if (time_before(refresh_time, *next_wake_time)) { + *next_wake_time =3D refresh_time; + } + } + + cond_resched(); + } while ((memcg =3D mem_cgroup_iter(NULL, memcg, NULL))); + + return should_wait; +} + +static int do_aging(void *unused) +{ + while (!kthread_should_stop()) { + int nid; + long timeout_ticks; + unsigned long next_wake_time; + bool should_wait =3D true; + + WRITE_ONCE(refresh_pending, false); + for_each_node_state(nid, N_MEMORY) { + unsigned long node_next_wake_time; + + if (do_aging_node(nid, &node_next_wake_time)) + continue; + if (should_wait) { + should_wait =3D false; + next_wake_time =3D node_next_wake_time; + } else if (time_before(node_next_wake_time, + next_wake_time)) { + next_wake_time =3D node_next_wake_time; + } + } + + if (should_wait) { + wait_event_interruptible(aging_wait, refresh_pending); + continue; + } + + /* sleep until next aging */ + timeout_ticks =3D next_wake_time - jiffies; + if (timeout_ticks > 0 && + timeout_ticks !=3D MAX_SCHEDULE_TIMEOUT) { + schedule_timeout_idle(timeout_ticks); + continue; + } + } + return 0; +} + +/* Invoked when refresh_interval shortens or changes to a non-zero value. = */ +void wsr_wakeup_aging_thread(void) +{ + WRITE_ONCE(refresh_pending, true); + wake_up_interruptible(&aging_wait); +} + +static struct task_struct *aging_thread; + +static int aging_init(void) +{ + struct task_struct *task; + + task =3D kthread_run(do_aging, NULL, "kagingd"); + + if (IS_ERR(task)) { + pr_err("Failed to create aging kthread\n"); + return PTR_ERR(task); + } + + aging_thread =3D task; + pr_info("module loaded\n"); + return 0; +} + +static void aging_exit(void) +{ + kthread_stop(aging_thread); + aging_thread =3D NULL; + pr_info("module unloaded\n"); +} + +module_init(aging_init); +module_exit(aging_exit); --=20 2.47.0.338.g60cca15819-goog