linux/include/linux/quicklist.h
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   1#ifndef LINUX_QUICKLIST_H
   2#define LINUX_QUICKLIST_H
   3/*
   4 * Fast allocations and disposal of pages. Pages must be in the condition
   5 * as needed after allocation when they are freed. Per cpu lists of pages
   6 * are kept that only contain node local pages.
   7 *
   8 * (C) 2007, SGI. Christoph Lameter <clameter@sgi.com>
   9 */
  10#include <linux/kernel.h>
  11#include <linux/gfp.h>
  12#include <linux/percpu.h>
  13
  14#ifdef CONFIG_QUICKLIST
  15
  16struct quicklist {
  17        void *page;
  18        int nr_pages;
  19};
  20
  21DECLARE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];
  22
  23/*
  24 * The two key functions quicklist_alloc and quicklist_free are inline so
  25 * that they may be custom compiled for the platform.
  26 * Specifying a NULL ctor can remove constructor support. Specifying
  27 * a constant quicklist allows the determination of the exact address
  28 * in the per cpu area.
  29 *
  30 * The fast patch in quicklist_alloc touched only a per cpu cacheline and
  31 * the first cacheline of the page itself. There is minmal overhead involved.
  32 */
  33static inline void *quicklist_alloc(int nr, gfp_t flags, void (*ctor)(void *))
  34{
  35        struct quicklist *q;
  36        void **p = NULL;
  37
  38        q =&get_cpu_var(quicklist)[nr];
  39        p = q->page;
  40        if (likely(p)) {
  41                q->page = p[0];
  42                p[0] = NULL;
  43                q->nr_pages--;
  44        }
  45        put_cpu_var(quicklist);
  46        if (likely(p))
  47                return p;
  48
  49        p = (void *)__get_free_page(flags | __GFP_ZERO);
  50        if (ctor && p)
  51                ctor(p);
  52        return p;
  53}
  54
  55static inline void __quicklist_free(int nr, void (*dtor)(void *), void *p,
  56        struct page *page)
  57{
  58        struct quicklist *q;
  59
  60        q = &get_cpu_var(quicklist)[nr];
  61        *(void **)p = q->page;
  62        q->page = p;
  63        q->nr_pages++;
  64        put_cpu_var(quicklist);
  65}
  66
  67static inline void quicklist_free(int nr, void (*dtor)(void *), void *pp)
  68{
  69        __quicklist_free(nr, dtor, pp, virt_to_page(pp));
  70}
  71
  72static inline void quicklist_free_page(int nr, void (*dtor)(void *),
  73                                                        struct page *page)
  74{
  75        __quicklist_free(nr, dtor, page_address(page), page);
  76}
  77
  78void quicklist_trim(int nr, void (*dtor)(void *),
  79        unsigned long min_pages, unsigned long max_free);
  80
  81unsigned long quicklist_total_size(void);
  82
  83#else
  84
  85static inline unsigned long quicklist_total_size(void)
  86{
  87        return 0;
  88}
  89
  90#endif
  91
  92#endif /* LINUX_QUICKLIST_H */
  93
  94
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