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
  22 DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];
  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
  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
  36 static 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  */
  49 void 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
  75 unsigned 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