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/mm.h>
  18#include <linux/mmzone.h>
  19#include <linux/module.h>
  20#include <linux/quicklist.h>
  21
  22DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];
  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        struct zone *zones = NODE_DATA(numa_node_id())->node_zones;
  30
  31        node_free_pages =
  32#ifdef CONFIG_ZONE_DMA
  33                zone_page_state(&zones[ZONE_DMA], NR_FREE_PAGES) +
  34#endif
  35#ifdef CONFIG_ZONE_DMA32
  36                zone_page_state(&zones[ZONE_DMA32], NR_FREE_PAGES) +
  37#endif
  38                zone_page_state(&zones[ZONE_NORMAL], NR_FREE_PAGES);
  39
  40        max = node_free_pages / FRACTION_OF_NODE_MEM;
  41        return max(max, min_pages);
  42}
  43
  44static long min_pages_to_free(struct quicklist *q,
  45        unsigned long min_pages, long max_free)
  46{
  47        long pages_to_free;
  48
  49        pages_to_free = q->nr_pages - max_pages(min_pages);
  50
  51        return min(pages_to_free, max_free);
  52}
  53
  54/*
  55 * Trim down the number of pages in the quicklist
  56 */
  57void quicklist_trim(int nr, void (*dtor)(void *),
  58        unsigned long min_pages, unsigned long max_free)
  59{
  60        long pages_to_free;
  61        struct quicklist *q;
  62
  63        q = &get_cpu_var(quicklist)[nr];
  64        if (q->nr_pages > min_pages) {
  65                pages_to_free = min_pages_to_free(q, min_pages, max_free);
  66
  67                while (pages_to_free > 0) {
  68                        /*
  69                         * We pass a gfp_t of 0 to quicklist_alloc here
  70                         * because we will never call into the page allocator.
  71                         */
  72                        void *p = quicklist_alloc(nr, 0, NULL);
  73
  74                        if (dtor)
  75                                dtor(p);
  76                        free_page((unsigned long)p);
  77                        pages_to_free--;
  78                }
  79        }
  80        put_cpu_var(quicklist);
  81}
  82
  83unsigned long quicklist_total_size(void)
  84{
  85        unsigned long count = 0;
  86        int cpu;
  87        struct quicklist *ql, *q;
  88
  89        for_each_online_cpu(cpu) {
  90                ql = per_cpu(quicklist, cpu);
  91                for (q = ql; q < ql + CONFIG_NR_QUICK; q++)
  92                        count += q->nr_pages;
  93        }
  94        return count;
  95}
  96
  97