Root/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/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
104

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