git.sesse.net Git - bcachefs-tools-debian/blob - linux/shrinker.c

   1
   2 #include <stdio.h>
   3
   4 #include <linux/list.h>
   5 #include <linux/mm.h>
   6 #include <linux/mutex.h>
   7 #include <linux/shrinker.h>
   8
   9 #include "tools-util.h"
  10
  11 static LIST_HEAD(shrinker_list);
  12 static DEFINE_MUTEX(shrinker_lock);
  13
  14 int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
  15 {
  16         mutex_lock(&shrinker_lock);
  17         list_add_tail(&shrinker->list, &shrinker_list);
  18         mutex_unlock(&shrinker_lock);
  19         return 0;
  20 }
  21
  22 void unregister_shrinker(struct shrinker *shrinker)
  23 {
  24         mutex_lock(&shrinker_lock);
  25         list_del(&shrinker->list);
  26         mutex_unlock(&shrinker_lock);
  27 }
  28
  29 struct meminfo {
  30         u64             total;
  31         u64             available;
  32 };
  33
  34 static u64 parse_meminfo_line(const char *line)
  35 {
  36         u64 v;
  37
  38         if (sscanf(line, " %llu kB", &v) < 1)
  39                 die("sscanf error");
  40         return v << 10;
  41 }
  42
  43 void si_meminfo(struct sysinfo *val)
  44 {
  45         size_t len, n = 0;
  46         char *line = NULL;
  47         const char *v;
  48         FILE *f;
  49
  50         memset(val, 0, sizeof(*val));
  51
  52         f = fopen("/proc/meminfo", "r");
  53         if (!f)
  54                 return;
  55
  56         while ((len = getline(&line, &n, f)) != -1) {
  57                 if ((v = strcmp_prefix(line, "MemTotal:")))
  58                         val->totalram = parse_meminfo_line(v);
  59
  60                 if ((v = strcmp_prefix(line, "MemAvailable:")))
  61                         val->freeram = parse_meminfo_line(v);
  62         }
  63
  64         fclose(f);
  65         free(line);
  66 }
  67
  68 static void run_shrinkers_allocation_failed(gfp_t gfp_mask)
  69 {
  70         struct shrinker *shrinker;
  71
  72         mutex_lock(&shrinker_lock);
  73         list_for_each_entry(shrinker, &shrinker_list, list) {
  74                 struct shrink_control sc = { .gfp_mask  = gfp_mask, };
  75
  76                 unsigned long have = shrinker->count_objects(shrinker, &sc);
  77
  78                 sc.nr_to_scan = have / 8;
  79
  80                 shrinker->scan_objects(shrinker, &sc);
  81         }
  82         mutex_unlock(&shrinker_lock);
  83 }
  84
  85 void run_shrinkers(gfp_t gfp_mask, bool allocation_failed)
  86 {
  87         struct shrinker *shrinker;
  88         struct sysinfo info;
  89         s64 want_shrink;
  90
  91         if (!(gfp_mask & GFP_KERNEL))
  92                 return;
  93
  94         /* Fast out if there are no shrinkers to run. */
  95         if (list_empty(&shrinker_list))
  96                 return;
  97
  98         if (allocation_failed) {
  99                 run_shrinkers_allocation_failed(gfp_mask);
 100                 return;
 101         }
 102
 103         si_meminfo(&info);
 104
 105         if (info.totalram && info.freeram) {
 106                 want_shrink = (info.totalram >> 2) - info.freeram;
 107
 108                 if (want_shrink <= 0)
 109                         return;
 110         } else {
 111                 /* If we weren't able to read /proc/meminfo, we must be pretty
 112                  * low: */
 113
 114                 want_shrink = 8 << 20;
 115         }
 116
 117         mutex_lock(&shrinker_lock);
 118         list_for_each_entry(shrinker, &shrinker_list, list) {
 119                 struct shrink_control sc = {
 120                         .gfp_mask       = gfp_mask,
 121                         .nr_to_scan     = want_shrink >> PAGE_SHIFT
 122                 };
 123
 124                 shrinker->scan_objects(shrinker, &sc);
 125         }
 126         mutex_unlock(&shrinker_lock);
 127 }