最新的内核已经pcp只有一个了

struct per_cpu_pageset {
     struct per_cpu_pages pcp;    
     s8 stat_threshold;
     s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
} ____cacheline_aligned_in_smp;

struct per_cpu_pages {
        int count;                /* number of pages in the list */
        int high;                /* high watermark, emptying needed */
        int batch;                /* chunk size for buddy add/remove */

        /* Lists of pages, one per migrate type stored on the pcp-lists */
        struct list_head lists[MIGRATE_PCPTYPES];
};


#define MIGRATE_PCPTYPES      3 /* the number of types on the pcp lists */

static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
{
        struct per_cpu_pages *pcp;
        int migratetype;

        memset(p, 0, sizeof(*p));

        pcp = &p->pcp;
        pcp->count = 0;
        pcp->high = 6 * batch;
        pcp->batch = max(1UL, 1 * batch);
        for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
                INIT_LIST_HEAD(&pcp->lists[migratetype]);
}

batch 这个参数是这样计算出来的
static int zone_batchsize(struct zone *zone)
{
#ifdef CONFIG_MMU

        int batch;
        batch = zone->present_pages / 1024;
        if (batch * PAGE_SIZE > 512 * 1024)
                batch = (512 * 1024) / PAGE_SIZE;
        batch /= 4;                /* We effectively *= 4 below */
        if (batch < 1)
                batch = 1;

        batch = rounddown_pow_of_two(batch + batch/2) - 1;

        return batch;

#else

        return 0;
#endif
}