This is an attempt to implement David Rientjes' idea of mempressure cgroup.

The main characteristics are the same to what I've tried to add to vmevent API:

Internally, it uses Mel Gorman's idea of scanned/reclaimed ratio for pressure index calculation. But we don't expose the index to the userland. Instead, there are three levels of the pressure:

o low (just reclaiming, e.g. caches are draining); o medium (allocation cost becomes high, e.g. swapping); o oom (about to oom very soon).

The rationale behind exposing levels and not the raw pressure index described here: http://lkml.org/lkml/2012/11/16/675

The API uses standard cgroups eventfd notifications:

$ gcc Documentation/cgroups/cgroup_event_listener.c -o \ cgroup_event_listener $ cd /sys/fs/cgroup/ $ mkdir mempressure $ mount -t cgroup cgroup ./mempressure -o mempressure $ cd mempressure $ cgroup_event_listener ./mempressure.level low ("low", "medium", "oom" are permitted values.)

Upon hitting the threshold, you should see "/sys/fs/cgroup/mempressure low: crossed" messages.

To test that it actually works on per-cgroup basis, I did a small trick: I moved all kswapd into a separate cgroup, and hooked the listener onto another (non-root) cgroup. The listener no longer received global reclaim pressure, which is expected.

For a task it is possible to be in both cpusets, memcg and mempressure cgroups, so by rearranging the tasks it should be possible to watch a specific pressure.

Note that while this adds the cgroups support, the code is well separated and eventually we might add a lightweight, non-cgroups API, i.e. vmevent. But this is another story.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org --- include/linux/cgroup_subsys.h | 6 + include/linux/vmstat.h | 8 ++ init/Kconfig | 5 + mm/Makefile | 1 + mm/mempressure.c | 287 ++++++++++++++++++++++++++++++++++++++++++ mm/vmscan.c | 3 + 6 files changed, 310 insertions(+) create mode 100644 mm/mempressure.c

diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h index f204a7a..b9802e2 100644 --- a/include/linux/cgroup_subsys.h +++ b/include/linux/cgroup_subsys.h @@ -37,6 +37,12 @@ SUBSYS(mem_cgroup)

/* */

+#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_MEMPRESSURE) +SUBSYS(mpc_cgroup) +#endif + +/* */ + #if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEVICE) SUBSYS(devices) #endif diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index 92a86b2..7698341 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -10,6 +10,14 @@

extern int sysctl_stat_interval;

+#ifdef CONFIG_CGROUP_MEMPRESSURE +extern void vmpressure(ulong scanned, ulong reclaimed); +extern void vmpressure_prio(int prio); +#else +static inline void vmpressure(ulong scanned, ulong reclaimed) {} +static inline void vmpressure_prio(int prio) {} +#endif + #ifdef CONFIG_VM_EVENT_COUNTERS /* * Light weight per cpu counter implementation. diff --git a/init/Kconfig b/init/Kconfig index 6fdd6e3..7065e44 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -826,6 +826,11 @@ config MEMCG_KMEM the kmem extension can use it to guarantee that no group of processes will ever exhaust kernel resources alone.

+config CGROUP_MEMPRESSURE + bool "Memory pressure monitor for Control Groups" + help + TODO + config CGROUP_HUGETLB bool "HugeTLB Resource Controller for Control Groups" depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL diff --git a/mm/Makefile b/mm/Makefile index 6b025f8..40cee19 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -50,6 +50,7 @@ obj-$(CONFIG_MIGRATION) += migrate.o obj-$(CONFIG_QUICKLIST) += quicklist.o obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o obj-$(CONFIG_MEMCG) += memcontrol.o page_cgroup.o +obj-$(CONFIG_CGROUP_MEMPRESSURE) += mempressure.o obj-$(CONFIG_CGROUP_HUGETLB) += hugetlb_cgroup.o obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o diff --git a/mm/mempressure.c b/mm/mempressure.c new file mode 100644 index 0000000..5c85bbe --- /dev/null +++ b/mm/mempressure.c @@ -0,0 +1,287 @@ +/* + * Linux VM pressure notifications + * + * Copyright 2012 Linaro Ltd. + * Anton Vorontsov anton.vorontsov@linaro.org + * + * Based on ideas from David Rientjes, KOSAKI Motohiro, Leonid Moiseichuk, + * Mel Gorman, Minchan Kim and Pekka Enberg. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published + * by the Free Software Foundation. + */ + +#include <linux/cgroup.h> +#include <linux/fs.h> +#include <linux/sched.h> +#include <linux/mm.h> +#include <linux/vmstat.h> +#include <linux/atomic.h> +#include <linux/eventfd.h> +#include <linux/swap.h> +#include <linux/printk.h> + +static void mpc_vmpressure(ulong scanned, ulong reclaimed); + +/* + * Generic VM Pressure routines (no cgroups or any other API details) + */ + +/* These are defaults. Might make them configurable one day. */ +static const uint vmpressure_win = SWAP_CLUSTER_MAX * 16; +static const uint vmpressure_level_med = 60; +static const uint vmpressure_level_oom = 99; +static const uint vmpressure_level_oom_prio = 4; + +enum vmpressure_levels { + VMPRESSURE_LOW = 0, + VMPRESSURE_MEDIUM, + VMPRESSURE_OOM, + VMPRESSURE_NUM_LEVELS, +}; + +static const char const *vmpressure_str_levels[] = { + [VMPRESSURE_LOW] = "low", + [VMPRESSURE_MEDIUM] = "medium", + [VMPRESSURE_OOM] = "oom", +}; + +static enum vmpressure_levels vmpressure_level(uint pressure) +{ + if (pressure >= vmpressure_level_oom) + return VMPRESSURE_OOM; + else if (pressure >= vmpressure_level_med) + return VMPRESSURE_MEDIUM; + return VMPRESSURE_LOW; +} + +static ulong vmpressure_calc_level(uint win, uint s, uint r) +{ + ulong p; + + if (!s) + return 0; + + /* + * We calculate the ratio (in percents) of how many pages were + * scanned vs. reclaimed in a given time frame (window). Note that + * time is in VM reclaimer's "ticks", i.e. number of pages + * scanned. This makes it possible to set desired reaction time + * and serves as a ratelimit. + */ + p = win - (r * win / s); + p = p * 100 / win; + + pr_debug("%s: %3lu (s: %6u r: %6u)\n", __func__, p, s, r); + + return vmpressure_level(p); +} + +void vmpressure(ulong scanned, ulong reclaimed) +{ + if (!scanned) + return; + mpc_vmpressure(scanned, reclaimed); +} + +void vmpressure_prio(int prio) +{ + if (prio > vmpressure_level_oom_prio) + return; + + /* OK, the prio is below the threshold, send the pre-OOM event. */ + vmpressure(vmpressure_win, 0); +} + +/* + * Memory pressure cgroup code + */ + +struct mpc_state { + struct cgroup_subsys_state css; + uint scanned; + uint reclaimed; + struct mutex lock; + struct eventfd_ctx *eventfd; + enum vmpressure_levels thres; +}; + +static struct mpc_state *css2mpc(struct cgroup_subsys_state *css) +{ + return container_of(css, struct mpc_state, css); +} + +static struct mpc_state *tsk2mpc(struct task_struct *tsk) +{ + return css2mpc(task_subsys_state(tsk, mpc_cgroup_subsys_id)); +} + +static struct mpc_state *cg2mpc(struct cgroup *cg) +{ + return css2mpc(cgroup_subsys_state(cg, mpc_cgroup_subsys_id)); +} + +static void __mpc_vmpressure(ulong scanned, ulong reclaimed) +{ + struct mpc_state *mpc = tsk2mpc(current); + int level; + + mpc->scanned += scanned; + mpc->reclaimed += reclaimed; + + if (mpc->scanned < vmpressure_win) + return; + + level = vmpressure_calc_level(vmpressure_win, + mpc->scanned, mpc->reclaimed); + if (level >= mpc->thres) { + mutex_lock(&mpc->lock); + if (mpc->eventfd) + eventfd_signal(mpc->eventfd, 1); + mutex_unlock(&mpc->lock); + } +} + +static void mpc_vmpressure(ulong scanned, ulong reclaimed) +{ + /* + * There are two options for implementing cgroup pressure + * notifications: + * + * - Store pressure counter atomically in the task struct. Upon + * hitting 'window' wake up a workqueue that will walk every + * task and sum per-thread pressure into cgroup pressure (to + * which the task belongs). The cons are obvious: bloats task + * struct, have to walk all processes and makes pressue less + * accurate (the window becomes per-thread); + * + * - Store pressure counters in per-cgroup state. This is easy and + * straighforward, and that's how we do things here. But this + * requires us to not put the vmpressure hooks into hotpath, + * since we have to grab some locks. + */ + task_lock(current); + __mpc_vmpressure(scanned, reclaimed); + task_unlock(current); +} + +static struct cgroup_subsys_state *mpc_create(struct cgroup *cg) +{ + struct mpc_state *mpc; + + mpc = kzalloc(sizeof(*mpc), GFP_KERNEL); + if (!mpc) + return ERR_PTR(-ENOMEM); + + mutex_init(&mpc->lock); + + return &mpc->css; +} + +static int mpc_pre_destroy(struct cgroup *cg) +{ + struct mpc_state *mpc = cg2mpc(cg); + int ret = 0; + + mutex_lock(&mpc->lock); + + if (mpc->eventfd) + ret = -EBUSY; + + mutex_unlock(&mpc->lock); + + return ret; +} + +static void mpc_destroy(struct cgroup *cg) +{ + struct mpc_state *mpc = cg2mpc(cg); + + kfree(mpc); +} + +static ssize_t mpc_read_level(struct cgroup *cg, struct cftype *cft, + struct file *file, char __user *buf, + size_t sz, loff_t *ppos) +{ + struct mpc_state *mpc = cg2mpc(cg); + uint level; + const char *str; + + mutex_lock(&mpc->lock); + + level = vmpressure_calc_level(vmpressure_win, + mpc->scanned, mpc->reclaimed); + mpc->scanned = 0; + mpc->reclaimed = 0; + + mutex_unlock(&mpc->lock); + + str = vmpressure_str_levels[level]; + return simple_read_from_buffer(buf, sz, ppos, str, strlen(str)); +} + +static int mpc_register_level_event(struct cgroup *cg, struct cftype *cft, + struct eventfd_ctx *eventfd, + const char *args) +{ + struct mpc_state *mpc = cg2mpc(cg); + int i; + int ret; + + mutex_lock(&mpc->lock); + + /* + * It's easy to implement multiple thresholds, but so far we don't + * need it. + */ + if (mpc->eventfd) { + ret = -EBUSY; + goto out_unlock; + } + + ret = -EINVAL; + for (i = 0; i < VMPRESSURE_NUM_LEVELS; i++) { + if (strcmp(vmpressure_str_levels[i], args)) + continue; + mpc->eventfd = eventfd; + mpc->thres = i; + ret = 0; + break; + } +out_unlock: + mutex_unlock(&mpc->lock); + + return ret; +} + +static void mpc_unregister_level_event(struct cgroup *cg, struct cftype *cft, + struct eventfd_ctx *eventfd) +{ + struct mpc_state *mpc = cg2mpc(cg); + + mutex_lock(&mpc->lock); + BUG_ON(mpc->eventfd != eventfd); + mpc->eventfd = NULL; + mutex_unlock(&mpc->lock); +} + +static struct cftype mpc_files[] = { + { + .name = "level", + .read = mpc_read_level, + .register_event = mpc_register_level_event, + .unregister_event = mpc_unregister_level_event, + }, + {}, +}; + +struct cgroup_subsys mpc_cgroup_subsys = { + .name = "mempressure", + .subsys_id = mpc_cgroup_subsys_id, + .create = mpc_create, + .pre_destroy = mpc_pre_destroy, + .destroy = mpc_destroy, + .base_cftypes = mpc_files, +}; diff --git a/mm/vmscan.c b/mm/vmscan.c index 48550c6..430d8a5 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1877,6 +1877,8 @@ restart: shrink_active_list(SWAP_CLUSTER_MAX, lruvec, sc, LRU_ACTIVE_ANON);

+ vmpressure(sc->nr_scanned - nr_scanned, nr_reclaimed); + /* reclaim/compaction might need reclaim to continue */ if (should_continue_reclaim(lruvec, nr_reclaimed, sc->nr_scanned - nr_scanned, sc)) @@ -2099,6 +2101,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, count_vm_event(ALLOCSTALL);

do { + vmpressure_prio(sc->priority); sc->nr_scanned = 0; aborted_reclaim = shrink_zones(zonelist, sc);