mm/allocpercpu.c

   1 /*
   2  * linux/mm/allocpercpu.c
   3  *
   4  * Separated from slab.c August 11, 2006 Christoph Lameter
   5  */
   6 #include <linux/mm.h>
   7 #include <linux/module.h>
   8
   9 #ifndef cache_line_size
  10 #define cache_line_size()       L1_CACHE_BYTES
  11 #endif
  12
  13 /**
  14  * percpu_depopulate - depopulate per-cpu data for given cpu
  15  * @__pdata: per-cpu data to depopulate
  16  * @cpu: depopulate per-cpu data for this cpu
  17  *
  18  * Depopulating per-cpu data for a cpu going offline would be a typical
  19  * use case. You need to register a cpu hotplug handler for that purpose.
  20  */
  21 static void percpu_depopulate(void *__pdata, int cpu)
  22 {
  23         struct percpu_data *pdata = __percpu_disguise(__pdata);
  24
  25         kfree(pdata->ptrs[cpu]);
  26         pdata->ptrs[cpu] = NULL;
  27 }
  28
  29 /**
  30  * percpu_depopulate_mask - depopulate per-cpu data for some cpu's
  31  * @__pdata: per-cpu data to depopulate
  32  * @mask: depopulate per-cpu data for cpu's selected through mask bits
  33  */
  34 static void __percpu_depopulate_mask(void *__pdata, const cpumask_t *mask)
  35 {
  36         int cpu;
  37         for_each_cpu_mask_nr(cpu, *mask)
  38                 percpu_depopulate(__pdata, cpu);
  39 }
  40
  41 #define percpu_depopulate_mask(__pdata, mask) \
  42         __percpu_depopulate_mask((__pdata), &(mask))
  43
  44 /**
  45  * percpu_populate - populate per-cpu data for given cpu
  46  * @__pdata: per-cpu data to populate further
  47  * @size: size of per-cpu object
  48  * @gfp: may sleep or not etc.
  49  * @cpu: populate per-data for this cpu
  50  *
  51  * Populating per-cpu data for a cpu coming online would be a typical
  52  * use case. You need to register a cpu hotplug handler for that purpose.
  53  * Per-cpu object is populated with zeroed buffer.
  54  */
  55 static void *percpu_populate(void *__pdata, size_t size, gfp_t gfp, int cpu)
  56 {
  57         struct percpu_data *pdata = __percpu_disguise(__pdata);
  58         int node = cpu_to_node(cpu);
  59
  60         /*
  61          * We should make sure each CPU gets private memory.
  62          */
  63         size = roundup(size, cache_line_size());
  64
  65         BUG_ON(pdata->ptrs[cpu]);
  66         if (node_online(node))
  67                 pdata->ptrs[cpu] = kmalloc_node(size, gfp|__GFP_ZERO, node);
  68         else
  69                 pdata->ptrs[cpu] = kzalloc(size, gfp);
  70         return pdata->ptrs[cpu];
  71 }
  72
  73 /**
  74  * percpu_populate_mask - populate per-cpu data for more cpu's
  75  * @__pdata: per-cpu data to populate further
  76  * @size: size of per-cpu object
  77  * @gfp: may sleep or not etc.
  78  * @mask: populate per-cpu data for cpu's selected through mask bits
  79  *
  80  * Per-cpu objects are populated with zeroed buffers.
  81  */
  82 static int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
  83                                   cpumask_t *mask)
  84 {
  85         cpumask_t populated;
  86         int cpu;
  87
  88         cpus_clear(populated);
  89         for_each_cpu_mask_nr(cpu, *mask)
  90                 if (unlikely(!percpu_populate(__pdata, size, gfp, cpu))) {
  91                         __percpu_depopulate_mask(__pdata, &populated);
  92                         return -ENOMEM;
  93                 } else
  94                         cpu_set(cpu, populated);
  95         return 0;
  96 }
  97
  98 #define percpu_populate_mask(__pdata, size, gfp, mask) \
  99         __percpu_populate_mask((__pdata), (size), (gfp), &(mask))
 100
 101 /**
 102  * alloc_percpu - initial setup of per-cpu data
 103  * @size: size of per-cpu object
 104  * @align: alignment
 105  *
 106  * Allocate dynamic percpu area.  Percpu objects are populated with
 107  * zeroed buffers.
 108  */
 109 void *__alloc_percpu(size_t size, size_t align)
 110 {
 111         /*
 112          * We allocate whole cache lines to avoid false sharing
 113          */
 114         size_t sz = roundup(nr_cpu_ids * sizeof(void *), cache_line_size());
 115         void *pdata = kzalloc(sz, GFP_KERNEL);
 116         void *__pdata = __percpu_disguise(pdata);
 117
 118         /*
 119          * Can't easily make larger alignment work with kmalloc.  WARN
 120          * on it.  Larger alignment should only be used for module
 121          * percpu sections on SMP for which this path isn't used.
 122          */
 123         WARN_ON_ONCE(align > SMP_CACHE_BYTES);
 124
 125         if (unlikely(!pdata))
 126                 return NULL;
 127         if (likely(!__percpu_populate_mask(__pdata, size, GFP_KERNEL,
 128                                            &cpu_possible_map)))
 129                 return __pdata;
 130         kfree(pdata);
 131         return NULL;
 132 }
 133 EXPORT_SYMBOL_GPL(__alloc_percpu);
 134
 135 /**
 136  * free_percpu - final cleanup of per-cpu data
 137  * @__pdata: object to clean up
 138  *
 139  * We simply clean up any per-cpu object left. No need for the client to
 140  * track and specify through a bis mask which per-cpu objects are to free.
 141  */
 142 void free_percpu(void *__pdata)
 143 {
 144         if (unlikely(!__pdata))
 145                 return;
 146         __percpu_depopulate_mask(__pdata, cpu_possible_mask);
 147         kfree(__percpu_disguise(__pdata));
 148 }
 149 EXPORT_SYMBOL_GPL(free_percpu);