root/mm/quicklist.c

DEFINITIONS

1. max_pages
2. min_pages_to_free
3. quicklist_trim
4. quicklist_total_size

/*
 * Quicklist support.
 *
 * Quicklists are light weight lists of pages that have a defined state
 * on alloc and free. Pages must be in the quicklist specific defined state
 * (zero by default) when the page is freed. It seems that the initial idea
 * for such lists first came from Dave Miller and then various other people
 * improved on it.
 *
 * Copyright (C) 2007 SGI,
 *      Christoph Lameter <clameter@sgi.com>
 *              Generalized, added support for multiple lists and
 *              constructors / destructors.
 */
#include <linux/kernel.h>

#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/module.h>
#include <linux/quicklist.h>

DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];

#define FRACTION_OF_NODE_MEM    16

static unsigned long max_pages(unsigned long min_pages)
{
        unsigned long node_free_pages, max;
        int node = numa_node_id();
        struct zone *zones = NODE_DATA(node)->node_zones;
        int num_cpus_on_node;
        node_to_cpumask_ptr(cpumask_on_node, node);

        node_free_pages =
#ifdef CONFIG_ZONE_DMA
                zone_page_state(&zones[ZONE_DMA], NR_FREE_PAGES) +
#endif
#ifdef CONFIG_ZONE_DMA32
                zone_page_state(&zones[ZONE_DMA32], NR_FREE_PAGES) +
#endif
                zone_page_state(&zones[ZONE_NORMAL], NR_FREE_PAGES);

        max = node_free_pages / FRACTION_OF_NODE_MEM;

        num_cpus_on_node = cpus_weight_nr(*cpumask_on_node);
        max /= num_cpus_on_node;

        return max(max, min_pages);
}

static long min_pages_to_free(struct quicklist *q,
        unsigned long min_pages, long max_free)
{
        long pages_to_free;

        pages_to_free = q->nr_pages - max_pages(min_pages);

        return min(pages_to_free, max_free);
}

/*
 * Trim down the number of pages in the quicklist
 */
void quicklist_trim(int nr, void (*dtor)(void *),
        unsigned long min_pages, unsigned long max_free)
{
        long pages_to_free;
        struct quicklist *q;

        q = &get_cpu_var(quicklist)[nr];
        if (q->nr_pages > min_pages) {
                pages_to_free = min_pages_to_free(q, min_pages, max_free);

                while (pages_to_free > 0) {
                        /*
                         * We pass a gfp_t of 0 to quicklist_alloc here
                         * because we will never call into the page allocator.
                         */
                        void *p = quicklist_alloc(nr, 0, NULL);

                        if (dtor)
                                dtor(p);
                        free_page((unsigned long)p);
                        pages_to_free--;
                }
        }
        put_cpu_var(quicklist);
}

unsigned long quicklist_total_size(void)
{
        unsigned long count = 0;
        int cpu;
        struct quicklist *ql, *q;

        for_each_online_cpu(cpu) {
                ql = per_cpu(quicklist, cpu);
                for (q = ql; q < ql + CONFIG_NR_QUICK; q++)
                        count += q->nr_pages;
        }
        return count;
}