mm/quicklist.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Quicklist support.
   4  *
   5  * Quicklists are light weight lists of pages that have a defined state
   6  * on alloc and free. Pages must be in the quicklist specific defined state
   7  * (zero by default) when the page is freed. It seems that the initial idea
   8  * for such lists first came from Dave Miller and then various other people
   9  * improved on it.
  10  *
  11  * Copyright (C) 2007 SGI,
  12  *      Christoph Lameter <cl@linux.com>
  13  *              Generalized, added support for multiple lists and
  14  *              constructors / destructors.
  15  */
  16 #include <linux/kernel.h>
  17
  18 #include <linux/gfp.h>
  19 #include <linux/mm.h>
  20 #include <linux/mmzone.h>
  21 #include <linux/quicklist.h>
  22
  23 DEFINE_PER_CPU(struct quicklist [CONFIG_NR_QUICK], quicklist);
  24
  25 #define FRACTION_OF_NODE_MEM    16
  26
  27 static unsigned long max_pages(unsigned long min_pages)
  28 {
  29         unsigned long node_free_pages, max;
  30         int node = numa_node_id();
  31         struct zone *zones = NODE_DATA(node)->node_zones;
  32         int num_cpus_on_node;
  33
  34         node_free_pages =
  35 #ifdef CONFIG_ZONE_DMA
  36                 zone_page_state(&zones[ZONE_DMA], NR_FREE_PAGES) +
  37 #endif
  38 #ifdef CONFIG_ZONE_DMA32
  39                 zone_page_state(&zones[ZONE_DMA32], NR_FREE_PAGES) +
  40 #endif
  41                 zone_page_state(&zones[ZONE_NORMAL], NR_FREE_PAGES);
  42
  43         max = node_free_pages / FRACTION_OF_NODE_MEM;
  44
  45         num_cpus_on_node = cpumask_weight(cpumask_of_node(node));
  46         max /= num_cpus_on_node;
  47
  48         return max(max, min_pages);
  49 }
  50
  51 static long min_pages_to_free(struct quicklist *q,
  52         unsigned long min_pages, long max_free)
  53 {
  54         long pages_to_free;
  55
  56         pages_to_free = q->nr_pages - max_pages(min_pages);
  57
  58         return min(pages_to_free, max_free);
  59 }
  60
  61 /*
  62  * Trim down the number of pages in the quicklist
  63  */
  64 void quicklist_trim(int nr, void (*dtor)(void *),
  65         unsigned long min_pages, unsigned long max_free)
  66 {
  67         long pages_to_free;
  68         struct quicklist *q;
  69
  70         q = &get_cpu_var(quicklist)[nr];
  71         if (q->nr_pages > min_pages) {
  72                 pages_to_free = min_pages_to_free(q, min_pages, max_free);
  73
  74                 while (pages_to_free > 0) {
  75                         /*
  76                          * We pass a gfp_t of 0 to quicklist_alloc here
  77                          * because we will never call into the page allocator.
  78                          */
  79                         void *p = quicklist_alloc(nr, 0, NULL);
  80
  81                         if (dtor)
  82                                 dtor(p);
  83                         free_page((unsigned long)p);
  84                         pages_to_free--;
  85                 }
  86         }
  87         put_cpu_var(quicklist);
  88 }
  89
  90 unsigned long quicklist_total_size(void)
  91 {
  92         unsigned long count = 0;
  93         int cpu;
  94         struct quicklist *ql, *q;
  95
  96         for_each_online_cpu(cpu) {
  97                 ql = per_cpu(quicklist, cpu);
  98                 for (q = ql; q < ql + CONFIG_NR_QUICK; q++)
  99                         count += q->nr_pages;
 100         }
 101         return count;
 102 }
 103