The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/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 
   22 DEFINE_PER_CPU(struct quicklist [CONFIG_NR_QUICK], quicklist);
   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         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 
   50 static 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  */
   63 void 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 
   89 unsigned 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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