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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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.
  */
 
 #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/slab.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 *vmpressure_parent(struct vmpressure *vmpr)
 {
     struct mem_cgroup *memcg = vmpressure_to_memcg(vmpr);
 
     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,
 };
 
 enum vmpressure_modes {
     VMPRESSURE_NO_PASSTHROUGH = 0,
     VMPRESSURE_HIERARCHY,
     VMPRESSURE_LOCAL,
     VMPRESSURE_NUM_MODES,
 };
 
 static const char * const vmpressure_str_levels[] = {
     [VMPRESSURE_LOW] = "low",
     [VMPRESSURE_MEDIUM] = "medium",
     [VMPRESSURE_CRITICAL] = "critical",
 };
 
 static const char * const vmpressure_str_modes[] = {
     [VMPRESSURE_NO_PASSTHROUGH] = "default",
     [VMPRESSURE_HIERARCHY] = "hierarchy",
     [VMPRESSURE_LOCAL] = "local",
 };
 
 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 = 0;
 
     /*
      * reclaimed can be greater than scanned for things such as reclaimed
      * slab pages. shrink_node() just adds reclaimed pages without a
      * related increment to scanned pages.
      */
     if (reclaimed >= scanned)
         goto out;
     /*
      * 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;
 
 out:
     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;
     enum vmpressure_modes mode;
     struct list_head node;
 };
 
 static bool vmpressure_event(struct vmpressure *vmpr,
                  const enum vmpressure_levels level,
                  bool ancestor, bool signalled)
 {
     struct vmpressure_event *ev;
     bool ret = false;
 
     mutex_lock(&vmpr->events_lock);
     list_for_each_entry(ev, &vmpr->events, node) {
         if (ancestor && ev->mode == VMPRESSURE_LOCAL)
             continue;
         if (signalled && ev->mode == VMPRESSURE_NO_PASSTHROUGH)
             continue;
         if (level < ev->level)
             continue;
         eventfd_signal(ev->efd, 1);
         ret = true;
     }
     mutex_unlock(&vmpr->events_lock);
 
     return ret;
 }
 
 static void vmpressure_work_fn(struct work_struct *work)
 {
     struct vmpressure *vmpr = work_to_vmpressure(work);
     unsigned long scanned;
     unsigned long reclaimed;
     enum vmpressure_levels level;
     bool ancestor = false;
     bool signalled = false;
 
     spin_lock(&vmpr->sr_lock);
     /*
      * 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.
      */
     scanned = vmpr->tree_scanned;
     if (!scanned) {
         spin_unlock(&vmpr->sr_lock);
         return;
     }
 
     reclaimed = vmpr->tree_reclaimed;
     vmpr->tree_scanned = 0;
     vmpr->tree_reclaimed = 0;
     spin_unlock(&vmpr->sr_lock);
 
     level = vmpressure_calc_level(scanned, reclaimed);
 
     do {
         if (vmpressure_event(vmpr, level, ancestor, signalled))
             signalled = true;
         ancestor = true;
     } while ((vmpr = vmpressure_parent(vmpr)));
 }
 
 /**
  * vmpressure() - Account memory pressure through scanned/reclaimed ratio
  * @gfp:    reclaimer's gfp mask
  * @memcg:  cgroup memory controller handle
  * @tree:   legacy subtree mode
  * @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.
  *
  * If @tree is set, vmpressure is in traditional userspace reporting
  * mode: @memcg is considered the pressure root and userspace is
  * notified of the entire subtree's reclaim efficiency.
  *
  * If @tree is not set, reclaim efficiency is recorded for @memcg, and
  * only in-kernel users are notified.
  *
  * This function does not return any value.
  */
 void vmpressure(gfp_t gfp, struct mem_cgroup *memcg, bool tree,
         unsigned long scanned, unsigned long reclaimed)
 {
     struct vmpressure *vmpr;
 
     if (mem_cgroup_disabled())
         return;
 
     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;
 
     if (tree) {
         spin_lock(&vmpr->sr_lock);
         scanned = vmpr->tree_scanned += scanned;
         vmpr->tree_reclaimed += reclaimed;
         spin_unlock(&vmpr->sr_lock);
 
         if (scanned < vmpressure_win)
             return;
         schedule_work(&vmpr->work);
     } else {
         enum vmpressure_levels level;
 
         /* For now, no users for root-level efficiency */
         if (!memcg || mem_cgroup_is_root(memcg))
             return;
 
         spin_lock(&vmpr->sr_lock);
         scanned = vmpr->scanned += scanned;
         reclaimed = vmpr->reclaimed += reclaimed;
         if (scanned < vmpressure_win) {
             spin_unlock(&vmpr->sr_lock);
             return;
         }
         vmpr->scanned = vmpr->reclaimed = 0;
         spin_unlock(&vmpr->sr_lock);
 
         level = vmpressure_calc_level(scanned, reclaimed);
 
         if (level > VMPRESSURE_LOW) {
             /*
              * Let the socket buffer allocator know that
              * we are having trouble reclaiming LRU pages.
              *
              * For hysteresis keep the pressure state
              * asserted for a second in which subsequent
              * pressure events can occur.
              */
             WRITE_ONCE(memcg->socket_pressure, jiffies + HZ);
         }
     }
 }
 
 /**
  * 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, true, vmpressure_win, 0);
 }
 
 #define MAX_VMPRESSURE_ARGS_LEN (strlen("critical") + strlen("hierarchy") + 2)
 
 /**
  * vmpressure_register_event() - Bind vmpressure notifications to an eventfd
  * @memcg:  memcg that is interested in vmpressure notifications
  * @eventfd:    eventfd context to link notifications with
  * @args:   event arguments (pressure level threshold, optional mode)
  *
  * This function associates eventfd context with the vmpressure
  * infrastructure, so that the notifications will be delivered to the
  * @eventfd. The @args parameter is a comma-delimited string that denotes a
  * pressure level threshold (one of vmpressure_str_levels, i.e. "low", "medium",
  * or "critical") and an optional mode (one of vmpressure_str_modes, i.e.
  * "hierarchy" or "local").
  *
  * To be used as memcg event method.
  *
  * Return: 0 on success, -ENOMEM on memory failure or -EINVAL if @args could
  * not be parsed.
  */
 int vmpressure_register_event(struct mem_cgroup *memcg,
                   struct eventfd_ctx *eventfd, const char *args)
 {
     struct vmpressure *vmpr = memcg_to_vmpressure(memcg);
     struct vmpressure_event *ev;
     enum vmpressure_modes mode = VMPRESSURE_NO_PASSTHROUGH;
     enum vmpressure_levels level;
     char *spec, *spec_orig;
     char *token;
     int ret = 0;
 
     spec_orig = spec = kstrndup(args, MAX_VMPRESSURE_ARGS_LEN, GFP_KERNEL);
     if (!spec)
         return -ENOMEM;
 
     /* Find required level */
     token = strsep(&spec, ",");
     ret = match_string(vmpressure_str_levels, VMPRESSURE_NUM_LEVELS, token);
     if (ret < 0)
         goto out;
     level = ret;
 
     /* Find optional mode */
     token = strsep(&spec, ",");
     if (token) {
         ret = match_string(vmpressure_str_modes, VMPRESSURE_NUM_MODES, token);
         if (ret < 0)
             goto out;
         mode = ret;
     }
 
     ev = kzalloc(sizeof(*ev), GFP_KERNEL);
     if (!ev) {
         ret = -ENOMEM;
         goto out;
     }
 
     ev->efd = eventfd;
     ev->level = level;
     ev->mode = mode;
 
     mutex_lock(&vmpr->events_lock);
     list_add(&ev->node, &vmpr->events);
     mutex_unlock(&vmpr->events_lock);
     ret = 0;
 out:
     kfree(spec_orig);
     return ret;
 }
 
 /**
  * vmpressure_unregister_event() - Unbind eventfd from vmpressure
  * @memcg:  memcg 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).
  *
  * To be used as memcg event method.
  */
 void vmpressure_unregister_event(struct mem_cgroup *memcg,
                  struct eventfd_ctx *eventfd)
 {
     struct vmpressure *vmpr = memcg_to_vmpressure(memcg);
     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)
 {
     spin_lock_init(&vmpr->sr_lock);
     mutex_init(&vmpr->events_lock);
     INIT_LIST_HEAD(&vmpr->events);
     INIT_WORK(&vmpr->work, vmpressure_work_fn);
 }
 
 /**
  * vmpressure_cleanup() - shuts down vmpressure control structure
  * @vmpr:   Structure to be cleaned up
  *
  * This function should be called before the structure in which it is
  * embedded is cleaned up.
  */
 void vmpressure_cleanup(struct vmpressure *vmpr)
 {
     /*
      * Make sure there is no pending work before eventfd infrastructure
      * goes away.
      */
     flush_work(&vmpr->work);
 }

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