4 files changed, 412 insertions, 1 deletions

diff --git a/mm/Makefile b/mm/Makefile
index 3a4628751f89..72c5acb9345f 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -50,7 +50,7 @@ obj-$(CONFIG_FS_XIP) += filemap_xip.o
 obj-$(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_MEMCG) += memcontrol.o page_cgroup.o vmpressure.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/memcontrol.c b/mm/memcontrol.c
index 7e5bc43c2d1f..360464f40e96 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -49,6 +49,7 @@
 #include <linux/fs.h>
 #include <linux/seq_file.h>
 #include <linux/vmalloc.h>
+#include <linux/vmpressure.h>
 #include <linux/mm_inline.h>
 #include <linux/page_cgroup.h>
 #include <linux/cpu.h>
@@ -261,6 +262,9 @@ struct mem_cgroup {
          */
         struct res_counter res;
 
+        /* vmpressure notifications */
+        struct vmpressure vmpressure;
+
         union {
                 /*
                  * the counter to account for mem+swap usage.
@@ -359,6 +363,7 @@ struct mem_cgroup {
         atomic_t        numainfo_events;
         atomic_t        numainfo_updating;
 #endif
+
         /*
          * Per cgroup active and inactive list, similar to the
          * per zone LRU lists.
@@ -510,6 +515,24 @@ struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
         return container_of(s, struct mem_cgroup, css);
 }
 
+/* Some nice accessors for the vmpressure. */
+struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg)
+{
+        if (!memcg)
+                memcg = root_mem_cgroup;
+        return &memcg->vmpressure;
+}
+
+struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr)
+{
+        return &container_of(vmpr, struct mem_cgroup, vmpressure)->css;
+}
+
+struct vmpressure *css_to_vmpressure(struct cgroup_subsys_state *css)
+{
+        return &mem_cgroup_from_css(css)->vmpressure;
+}
+
 static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
 {
         return (memcg == root_mem_cgroup);
@@ -5907,6 +5930,11 @@ static struct cftype mem_cgroup_files[] = {
                 .unregister_event = mem_cgroup_oom_unregister_event,
                 .private = MEMFILE_PRIVATE(_OOM_TYPE, OOM_CONTROL),
         },
+        {
+                .name = "pressure_level",
+                .register_event = vmpressure_register_event,
+                .unregister_event = vmpressure_unregister_event,
+        },
 #ifdef CONFIG_NUMA
         {
                 .name = "numa_stat",
@@ -6188,6 +6216,7 @@ mem_cgroup_css_alloc(struct cgroup *cont)
         memcg->move_charge_at_immigrate = 0;
         mutex_init(&memcg->thresholds_lock);
         spin_lock_init(&memcg->move_lock);
+        vmpressure_init(&memcg->vmpressure);
 
         return &memcg->css;
 
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
new file mode 100644
index 000000000000..736a6011c2c8
--- /dev/null
+++ b/mm/vmpressure.c
@@ -0,0 +1,374 @@
+/*
+ * Linux VM pressure
+ *
+ * Copyright 2012 Linaro Ltd.
+ *                Anton Vorontsov <anton.vorontsov@linaro.org>
+ *
+ * Based on ideas from Andrew Morton, 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/log2.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/vmstat.h>
+#include <linux/eventfd.h>
+#include <linux/swap.h>
+#include <linux/printk.h>
+#include <linux/vmpressure.h>
+
+/*
+ * The window size (vmpressure_win) is the number of scanned pages before
+ * we try to analyze scanned/reclaimed ratio. So the window is used as a
+ * rate-limit tunable for the "low" level notification, and also for
+ * averaging the ratio for medium/critical levels. Using small window
+ * sizes can cause lot of false positives, but too big window size will
+ * delay the notifications.
+ *
+ * As the vmscan reclaimer logic works with chunks which are multiple of
+ * SWAP_CLUSTER_MAX, it makes sense to use it for the window size as well.
+ *
+ * TODO: Make the window size depend on machine size, as we do for vmstat
+ * thresholds. Currently we set it to 512 pages (2MB for 4KB pages).
+ */
+static const unsigned long vmpressure_win = SWAP_CLUSTER_MAX * 16;
+
+/*
+ * These thresholds are used when we account memory pressure through
+ * scanned/reclaimed ratio. The current values were chosen empirically. In
+ * essence, they are percents: the higher the value, the more number
+ * unsuccessful reclaims there were.
+ */
+static const unsigned int vmpressure_level_med = 60;
+static const unsigned int vmpressure_level_critical = 95;
+
+/*
+ * When there are too little pages left to scan, vmpressure() may miss the
+ * critical pressure as number of pages will be less than "window size".
+ * However, in that case the vmscan priority will raise fast as the
+ * reclaimer will try to scan LRUs more deeply.
+ *
+ * The vmscan logic considers these special priorities:
+ *
+ * prio == DEF_PRIORITY (12): reclaimer starts with that value
+ * prio <= DEF_PRIORITY - 2 : kswapd becomes somewhat overwhelmed
+ * prio == 0                : close to OOM, kernel scans every page in an lru
+ *
+ * Any value in this range is acceptable for this tunable (i.e. from 12 to
+ * 0). Current value for the vmpressure_level_critical_prio is chosen
+ * empirically, but the number, in essence, means that we consider
+ * critical level when scanning depth is ~10% of the lru size (vmscan
+ * scans 'lru_size >> prio' pages, so it is actually 12.5%, or one
+ * eights).
+ */
+static const unsigned int vmpressure_level_critical_prio = ilog2(100 / 10);
+
+static struct vmpressure *work_to_vmpressure(struct work_struct *work)
+{
+        return container_of(work, struct vmpressure, work);
+}
+
+static struct vmpressure *cg_to_vmpressure(struct cgroup *cg)
+{
+        return css_to_vmpressure(cgroup_subsys_state(cg, mem_cgroup_subsys_id));
+}
+
+static struct vmpressure *vmpressure_parent(struct vmpressure *vmpr)
+{
+        struct cgroup *cg = vmpressure_to_css(vmpr)->cgroup;
+        struct mem_cgroup *memcg = mem_cgroup_from_cont(cg);
+
+        memcg = parent_mem_cgroup(memcg);
+        if (!memcg)
+                return NULL;
+        return memcg_to_vmpressure(memcg);
+}
+
+enum vmpressure_levels {
+        VMPRESSURE_LOW = 0,
+        VMPRESSURE_MEDIUM,
+        VMPRESSURE_CRITICAL,
+        VMPRESSURE_NUM_LEVELS,
+};
+
+static const char * const vmpressure_str_levels[] = {
+        [VMPRESSURE_LOW] = "low",
+        [VMPRESSURE_MEDIUM] = "medium",
+        [VMPRESSURE_CRITICAL] = "critical",
+};
+
+static enum vmpressure_levels vmpressure_level(unsigned long pressure)
+{
+        if (pressure >= vmpressure_level_critical)
+                return VMPRESSURE_CRITICAL;
+        else if (pressure >= vmpressure_level_med)
+                return VMPRESSURE_MEDIUM;
+        return VMPRESSURE_LOW;
+}
+
+static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
+                                                    unsigned long reclaimed)
+{
+        unsigned long scale = scanned + reclaimed;
+        unsigned long pressure;
+
+        /*
+         * 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.
+         */
+        pressure = scale - (reclaimed * scale / scanned);
+        pressure = pressure * 100 / scale;
+
+        pr_debug("%s: %3lu  (s: %lu  r: %lu)\n", __func__, pressure,
+                 scanned, reclaimed);
+
+        return vmpressure_level(pressure);
+}
+
+struct vmpressure_event {
+        struct eventfd_ctx *efd;
+        enum vmpressure_levels level;
+        struct list_head node;
+};
+
+static bool vmpressure_event(struct vmpressure *vmpr,
+                             unsigned long scanned, unsigned long reclaimed)
+{
+        struct vmpressure_event *ev;
+        enum vmpressure_levels level;
+        bool signalled = false;
+
+        level = vmpressure_calc_level(scanned, reclaimed);
+
+        mutex_lock(&vmpr->events_lock);
+
+        list_for_each_entry(ev, &vmpr->events, node) {
+                if (level >= ev->level) {
+                        eventfd_signal(ev->efd, 1);
+                        signalled = true;
+                }
+        }
+
+        mutex_unlock(&vmpr->events_lock);
+
+        return signalled;
+}
+
+static void vmpressure_work_fn(struct work_struct *work)
+{
+        struct vmpressure *vmpr = work_to_vmpressure(work);
+        unsigned long scanned;
+        unsigned long reclaimed;
+
+        /*
+         * Several contexts might be calling vmpressure(), so it is
+         * possible that the work was rescheduled again before the old
+         * work context cleared the counters. In that case we will run
+         * just after the old work returns, but then scanned might be zero
+         * here. No need for any locks here since we don't care if
+         * vmpr->reclaimed is in sync.
+         */
+        if (!vmpr->scanned)
+                return;
+
+        mutex_lock(&vmpr->sr_lock);
+        scanned = vmpr->scanned;
+        reclaimed = vmpr->reclaimed;
+        vmpr->scanned = 0;
+        vmpr->reclaimed = 0;
+        mutex_unlock(&vmpr->sr_lock);
+
+        do {
+                if (vmpressure_event(vmpr, scanned, reclaimed))
+                        break;
+                /*
+                 * If not handled, propagate the event upward into the
+                 * hierarchy.
+                 */
+        } while ((vmpr = vmpressure_parent(vmpr)));
+}
+
+/**
+ * vmpressure() - Account memory pressure through scanned/reclaimed ratio
+ * @gfp:        reclaimer's gfp mask
+ * @memcg:      cgroup memory controller handle
+ * @scanned:    number of pages scanned
+ * @reclaimed:  number of pages reclaimed
+ *
+ * This function should be called from the vmscan reclaim path to account
+ * "instantaneous" memory pressure (scanned/reclaimed ratio). The raw
+ * pressure index is then further refined and averaged over time.
+ *
+ * This function does not return any value.
+ */
+void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
+                unsigned long scanned, unsigned long reclaimed)
+{
+        struct vmpressure *vmpr = memcg_to_vmpressure(memcg);
+
+        /*
+         * Here we only want to account pressure that userland is able to
+         * help us with. For example, suppose that DMA zone is under
+         * pressure; if we notify userland about that kind of pressure,
+         * then it will be mostly a waste as it will trigger unnecessary
+         * freeing of memory by userland (since userland is more likely to
+         * have HIGHMEM/MOVABLE pages instead of the DMA fallback). That
+         * is why we include only movable, highmem and FS/IO pages.
+         * Indirect reclaim (kswapd) sets sc->gfp_mask to GFP_KERNEL, so
+         * we account it too.
+         */
+        if (!(gfp & (__GFP_HIGHMEM | __GFP_MOVABLE | __GFP_IO | __GFP_FS)))
+                return;
+
+        /*
+         * If we got here with no pages scanned, then that is an indicator
+         * that reclaimer was unable to find any shrinkable LRUs at the
+         * current scanning depth. But it does not mean that we should
+         * report the critical pressure, yet. If the scanning priority
+         * (scanning depth) goes too high (deep), we will be notified
+         * through vmpressure_prio(). But so far, keep calm.
+         */
+        if (!scanned)
+                return;
+
+        mutex_lock(&vmpr->sr_lock);
+        vmpr->scanned += scanned;
+        vmpr->reclaimed += reclaimed;
+        scanned = vmpr->scanned;
+        mutex_unlock(&vmpr->sr_lock);
+
+        if (scanned < vmpressure_win || work_pending(&vmpr->work))
+                return;
+        schedule_work(&vmpr->work);
+}
+
+/**
+ * vmpressure_prio() - Account memory pressure through reclaimer priority level
+ * @gfp:        reclaimer's gfp mask
+ * @memcg:      cgroup memory controller handle
+ * @prio:       reclaimer's priority
+ *
+ * This function should be called from the reclaim path every time when
+ * the vmscan's reclaiming priority (scanning depth) changes.
+ *
+ * This function does not return any value.
+ */
+void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio)
+{
+        /*
+         * We only use prio for accounting critical level. For more info
+         * see comment for vmpressure_level_critical_prio variable above.
+         */
+        if (prio > vmpressure_level_critical_prio)
+                return;
+
+        /*
+         * OK, the prio is below the threshold, updating vmpressure
+         * information before shrinker dives into long shrinking of long
+         * range vmscan. Passing scanned = vmpressure_win, reclaimed = 0
+         * to the vmpressure() basically means that we signal 'critical'
+         * level.
+         */
+        vmpressure(gfp, memcg, vmpressure_win, 0);
+}
+
+/**
+ * vmpressure_register_event() - Bind vmpressure notifications to an eventfd
+ * @cg:         cgroup that is interested in vmpressure notifications
+ * @cft:        cgroup control files handle
+ * @eventfd:    eventfd context to link notifications with
+ * @args:       event arguments (used to set up a pressure level threshold)
+ *
+ * This function associates eventfd context with the vmpressure
+ * infrastructure, so that the notifications will be delivered to the
+ * @eventfd. The @args parameter is a string that denotes pressure level
+ * threshold (one of vmpressure_str_levels, i.e. "low", "medium", or
+ * "critical").
+ *
+ * This function should not be used directly, just pass it to (struct
+ * cftype).register_event, and then cgroup core will handle everything by
+ * itself.
+ */
+int vmpressure_register_event(struct cgroup *cg, struct cftype *cft,
+                              struct eventfd_ctx *eventfd, const char *args)
+{
+        struct vmpressure *vmpr = cg_to_vmpressure(cg);
+        struct vmpressure_event *ev;
+        int level;
+
+        for (level = 0; level < VMPRESSURE_NUM_LEVELS; level++) {
+                if (!strcmp(vmpressure_str_levels[level], args))
+                        break;
+        }
+
+        if (level >= VMPRESSURE_NUM_LEVELS)
+                return -EINVAL;
+
+        ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+        if (!ev)
+                return -ENOMEM;
+
+        ev->efd = eventfd;
+        ev->level = level;
+
+        mutex_lock(&vmpr->events_lock);
+        list_add(&ev->node, &vmpr->events);
+        mutex_unlock(&vmpr->events_lock);
+
+        return 0;
+}
+
+/**
+ * vmpressure_unregister_event() - Unbind eventfd from vmpressure
+ * @cg:         cgroup handle
+ * @cft:        cgroup control files handle
+ * @eventfd:    eventfd context that was used to link vmpressure with the @cg
+ *
+ * This function does internal manipulations to detach the @eventfd from
+ * the vmpressure notifications, and then frees internal resources
+ * associated with the @eventfd (but the @eventfd itself is not freed).
+ *
+ * This function should not be used directly, just pass it to (struct
+ * cftype).unregister_event, and then cgroup core will handle everything
+ * by itself.
+ */
+void vmpressure_unregister_event(struct cgroup *cg, struct cftype *cft,
+                                 struct eventfd_ctx *eventfd)
+{
+        struct vmpressure *vmpr = cg_to_vmpressure(cg);
+        struct vmpressure_event *ev;
+
+        mutex_lock(&vmpr->events_lock);
+        list_for_each_entry(ev, &vmpr->events, node) {
+                if (ev->efd != eventfd)
+                        continue;
+                list_del(&ev->node);
+                kfree(ev);
+                break;
+        }
+        mutex_unlock(&vmpr->events_lock);
+}
+
+/**
+ * vmpressure_init() - Initialize vmpressure control structure
+ * @vmpr:       Structure to be initialized
+ *
+ * This function should be called on every allocated vmpressure structure
+ * before any usage.
+ */
+void vmpressure_init(struct vmpressure *vmpr)
+{
+        mutex_init(&vmpr->sr_lock);
+        mutex_init(&vmpr->events_lock);
+        INIT_LIST_HEAD(&vmpr->events);
+        INIT_WORK(&vmpr->work, vmpressure_work_fn);
+}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index e03a00b09da9..e53e49584cf3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -19,6 +19,7 @@
 #include <linux/pagemap.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
+#include <linux/vmpressure.h>
 #include <linux/vmstat.h>
 #include <linux/file.h>
 #include <linux/writeback.h>
@@ -1982,6 +1983,11 @@ static void shrink_zone(struct zone *zone, struct scan_control *sc)
                         }
                         memcg = mem_cgroup_iter(root, memcg, &reclaim);
                 } while (memcg);
+
+                vmpressure(sc->gfp_mask, sc->target_mem_cgroup,
+                           sc->nr_scanned - nr_scanned,
+                           sc->nr_reclaimed - nr_reclaimed);
+
         } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed,
                                          sc->nr_scanned - nr_scanned, sc));
 }
@@ -2167,6 +2173,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
                 count_vm_event(ALLOCSTALL);
 
         do {
+                vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup,
+                                sc->priority);
                 sc->nr_scanned = 0;
                 aborted_reclaim = shrink_zones(zonelist, sc);