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