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/module.h>
  21#include <linux/quicklist.h>
  22
  23DEFINE_PER_CPU(struct quicklist [CONFIG_NR_QUICK], quicklist);
  24
  25#define FRACTION_OF_NODE_MEM    16
  26
  27static 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
  51static 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 */
  64void 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
  90unsigned 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
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