linux/mm/quicklist.c
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   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 <clameter@sgi.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
  22DEFINE_PER_CPU(struct quicklist [CONFIG_NR_QUICK], quicklist);
  23
  24#define FRACTION_OF_NODE_MEM    16
  25
  26static 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
  50static 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 */
  63void 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
  89unsigned 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
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