mm/quicklist.c

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