FreeBSD/Linux Kernel Cross Reference
sys/mm/allocpercpu.c

     /*
      * linux/mm/allocpercpu.c
      *
      * Separated from slab.c August 11, 2006 Christoph Lameter
      */
     #include <linux/mm.h>
     #include <linux/module.h>
     #include <linux/bootmem.h>
     #include <asm/sections.h>
    
    #ifndef cache_line_size
    #define cache_line_size()       L1_CACHE_BYTES
    #endif
    
    /**
     * percpu_depopulate - depopulate per-cpu data for given cpu
     * @__pdata: per-cpu data to depopulate
     * @cpu: depopulate per-cpu data for this cpu
     *
     * Depopulating per-cpu data for a cpu going offline would be a typical
     * use case. You need to register a cpu hotplug handler for that purpose.
     */
    static void percpu_depopulate(void *__pdata, int cpu)
    {
            struct percpu_data *pdata = __percpu_disguise(__pdata);
    
            kfree(pdata->ptrs[cpu]);
            pdata->ptrs[cpu] = NULL;
    }
    
    /**
     * percpu_depopulate_mask - depopulate per-cpu data for some cpu's
     * @__pdata: per-cpu data to depopulate
     * @mask: depopulate per-cpu data for cpu's selected through mask bits
     */
    static void __percpu_depopulate_mask(void *__pdata, const cpumask_t *mask)
    {
            int cpu;
            for_each_cpu_mask_nr(cpu, *mask)
                    percpu_depopulate(__pdata, cpu);
    }
    
    #define percpu_depopulate_mask(__pdata, mask) \
            __percpu_depopulate_mask((__pdata), &(mask))
    
    /**
     * percpu_populate - populate per-cpu data for given cpu
     * @__pdata: per-cpu data to populate further
     * @size: size of per-cpu object
     * @gfp: may sleep or not etc.
     * @cpu: populate per-data for this cpu
     *
     * Populating per-cpu data for a cpu coming online would be a typical
     * use case. You need to register a cpu hotplug handler for that purpose.
     * Per-cpu object is populated with zeroed buffer.
     */
    static void *percpu_populate(void *__pdata, size_t size, gfp_t gfp, int cpu)
    {
            struct percpu_data *pdata = __percpu_disguise(__pdata);
            int node = cpu_to_node(cpu);
    
            /*
             * We should make sure each CPU gets private memory.
             */
            size = roundup(size, cache_line_size());
    
            BUG_ON(pdata->ptrs[cpu]);
            if (node_online(node))
                    pdata->ptrs[cpu] = kmalloc_node(size, gfp|__GFP_ZERO, node);
            else
                    pdata->ptrs[cpu] = kzalloc(size, gfp);
            return pdata->ptrs[cpu];
    }
    
    /**
     * percpu_populate_mask - populate per-cpu data for more cpu's
     * @__pdata: per-cpu data to populate further
     * @size: size of per-cpu object
     * @gfp: may sleep or not etc.
     * @mask: populate per-cpu data for cpu's selected through mask bits
     *
     * Per-cpu objects are populated with zeroed buffers.
     */
    static int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
                                      cpumask_t *mask)
    {
            cpumask_t populated;
            int cpu;
    
            cpus_clear(populated);
            for_each_cpu_mask_nr(cpu, *mask)
                    if (unlikely(!percpu_populate(__pdata, size, gfp, cpu))) {
                            __percpu_depopulate_mask(__pdata, &populated);
                            return -ENOMEM;
                    } else
                            cpu_set(cpu, populated);
            return 0;
    }
    
   #define percpu_populate_mask(__pdata, size, gfp, mask) \
           __percpu_populate_mask((__pdata), (size), (gfp), &(mask))
   
   /**
    * alloc_percpu - initial setup of per-cpu data
    * @size: size of per-cpu object
    * @align: alignment
    *
    * Allocate dynamic percpu area.  Percpu objects are populated with
    * zeroed buffers.
    */
   void *__alloc_percpu(size_t size, size_t align)
   {
           /*
            * We allocate whole cache lines to avoid false sharing
            */
           size_t sz = roundup(nr_cpu_ids * sizeof(void *), cache_line_size());
           void *pdata = kzalloc(sz, GFP_KERNEL);
           void *__pdata = __percpu_disguise(pdata);
   
           /*
            * Can't easily make larger alignment work with kmalloc.  WARN
            * on it.  Larger alignment should only be used for module
            * percpu sections on SMP for which this path isn't used.
            */
           WARN_ON_ONCE(align > SMP_CACHE_BYTES);
   
           if (unlikely(!pdata))
                   return NULL;
           if (likely(!__percpu_populate_mask(__pdata, size, GFP_KERNEL,
                                              &cpu_possible_map)))
                   return __pdata;
           kfree(pdata);
           return NULL;
   }
   EXPORT_SYMBOL_GPL(__alloc_percpu);
   
   /**
    * free_percpu - final cleanup of per-cpu data
    * @__pdata: object to clean up
    *
    * We simply clean up any per-cpu object left. No need for the client to
    * track and specify through a bis mask which per-cpu objects are to free.
    */
   void free_percpu(void *__pdata)
   {
           if (unlikely(!__pdata))
                   return;
           __percpu_depopulate_mask(__pdata, cpu_possible_mask);
           kfree(__percpu_disguise(__pdata));
   }
   EXPORT_SYMBOL_GPL(free_percpu);
   
   /*
    * Generic percpu area setup.
    */
   #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
   unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
   
   EXPORT_SYMBOL(__per_cpu_offset);
   
   void __init setup_per_cpu_areas(void)
   {
           unsigned long size, i;
           char *ptr;
           unsigned long nr_possible_cpus = num_possible_cpus();
   
           /* Copy section for each CPU (we discard the original) */
           size = ALIGN(PERCPU_ENOUGH_ROOM, PAGE_SIZE);
           ptr = alloc_bootmem_pages(size * nr_possible_cpus);
   
           for_each_possible_cpu(i) {
                   __per_cpu_offset[i] = ptr - __per_cpu_start;
                   memcpy(ptr, __per_cpu_start, __per_cpu_end - __per_cpu_start);
                   ptr += size;
           }
   }
   #endif /* CONFIG_HAVE_SETUP_PER_CPU_AREA */

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