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[PATCH] CPU hotplug compatible alloc_percpu() 

This patch splits alloc_percpu() up into two phases.  Likewise for
free_percpu().  This allows clients to limit initial allocations to online
cpu's, and to populate or depopulate per-cpu data at run time as needed:

  struct my_struct *obj;

  /* initial allocation for online cpu's */
  obj = percpu_alloc(sizeof(struct my_struct), GFP_KERNEL);

  ...

  /* populate per-cpu data for cpu coming online */
  ptr = percpu_populate(obj, sizeof(struct my_struct), GFP_KERNEL, cpu);

  ...

  /* access per-cpu object */
  ptr = percpu_ptr(obj, smp_processor_id());

  ...

  /* depopulate per-cpu data for cpu going offline */
  percpu_depopulate(obj, cpu);

  ...

  /* final removal */
  percpu_free(obj);

Signed-off-by: Martin Peschke <mp3@de.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Martin Peschke 2006-09-25 23:31:21 -07:00 committed by Linus Torvalds
parent 8bc719d3ca
commit 7ff6f08295
2 changed files with 173 additions and 80 deletions
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79
include/linux/percpu.h
View File

@ -1,9 +1,12 @@
#ifndef __LINUX_PERCPU_H
#define __LINUX_PERCPU_H
#include <linux/spinlock.h> /* For preempt_disable() */
#include <linux/slab.h> /* For kmalloc() */
#include <linux/smp.h>
#include <linux/string.h> /* For memset() */
#include <linux/cpumask.h>
#include <asm/percpu.h>
/* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */
@ -27,39 +30,77 @@ struct percpu_data {
void *ptrs[NR_CPUS];
};
#define __percpu_disguise(pdata) (struct percpu_data *)~(unsigned long)(pdata)
/*
* Use this to get to a cpu's version of the per-cpu object allocated using
* alloc_percpu. Non-atomic access to the current CPU's version should
* Use this to get to a cpu's version of the per-cpu object dynamically
* allocated. Non-atomic access to the current CPU's version should
* probably be combined with get_cpu()/put_cpu().
*/
#define per_cpu_ptr(ptr, cpu) \
({ \
struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \
(__typeof__(ptr))__p->ptrs[(cpu)]; \
#define percpu_ptr(ptr, cpu) \
({ \
struct percpu_data *__p = __percpu_disguise(ptr); \
(__typeof__(ptr))__p->ptrs[(cpu)]; \
})
extern void *__alloc_percpu(size_t size);
extern void free_percpu(const void *);
extern void *percpu_populate(void *__pdata, size_t size, gfp_t gfp, int cpu);
extern void percpu_depopulate(void *__pdata, int cpu);
extern int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
cpumask_t *mask);
extern void __percpu_depopulate_mask(void *__pdata, cpumask_t *mask);
extern void *__percpu_alloc_mask(size_t size, gfp_t gfp, cpumask_t *mask);
extern void percpu_free(void *__pdata);
#else /* CONFIG_SMP */
#define per_cpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
#define percpu_ptr(ptr, cpu) ({ (void)(cpu); (ptr); })
static inline void *__alloc_percpu(size_t size)
static inline void percpu_depopulate(void *__pdata, int cpu)
{
void *ret = kmalloc(size, GFP_KERNEL);
if (ret)
memset(ret, 0, size);
return ret;
}
static inline void free_percpu(const void *ptr)
{
kfree(ptr);
static inline void __percpu_depopulate_mask(void *__pdata, cpumask_t *mask)
{
}
static inline void *percpu_populate(void *__pdata, size_t size, gfp_t gfp,
int cpu)
{
return percpu_ptr(__pdata, cpu);
}
static inline int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
cpumask_t *mask)
{
return 0;
}
static inline void *__percpu_alloc_mask(size_t size, gfp_t gfp, cpumask_t *mask)
{
return kzalloc(size, gfp);
}
static inline void percpu_free(void *__pdata)
{
kfree(__pdata);
}
#endif /* CONFIG_SMP */
/* Simple wrapper for the common case: zeros memory. */
#define alloc_percpu(type) ((type *)(__alloc_percpu(sizeof(type))))
#define percpu_populate_mask(__pdata, size, gfp, mask) \
__percpu_populate_mask((__pdata), (size), (gfp), &(mask))
#define percpu_depopulate_mask(__pdata, mask) \
__percpu_depopulate_mask((__pdata), &(mask))
#define percpu_alloc_mask(size, gfp, mask) \
__percpu_alloc_mask((size), (gfp), &(mask))
#define percpu_alloc(size, gfp) percpu_alloc_mask((size), (gfp), cpu_online_map)
/* (legacy) interface for use without CPU hotplug handling */
#define __alloc_percpu(size) percpu_alloc_mask((size), GFP_KERNEL, \
cpu_possible_map)
#define alloc_percpu(type) (type *)__alloc_percpu(sizeof(type))
#define free_percpu(ptr) percpu_free((ptr))
#define per_cpu_ptr(ptr, cpu) percpu_ptr((ptr), (cpu))
#endif /* __LINUX_PERCPU_H */

174
mm/slab.c
View File

@ -3371,52 +3371,127 @@ EXPORT_SYMBOL(__kmalloc_track_caller);
#ifdef CONFIG_SMP
/**
* __alloc_percpu - allocate one copy of the object for every present
* cpu in the system, zeroing them.
* Objects should be dereferenced using the per_cpu_ptr macro only.
* percpu_depopulate - depopulate per-cpu data for given cpu
* @__pdata: per-cpu data to depopulate
* @cpu: depopulate per-cpu data for this cpu
*
* @size: how many bytes of memory are required.
* 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.
*/
void *__alloc_percpu(size_t size)
void percpu_depopulate(void *__pdata, int cpu)
{
int i;
struct percpu_data *pdata = kmalloc(sizeof(*pdata), GFP_KERNEL);
struct percpu_data *pdata = __percpu_disguise(__pdata);
if (pdata->ptrs[cpu]) {
kfree(pdata->ptrs[cpu]);
pdata->ptrs[cpu] = NULL;
}
}
EXPORT_SYMBOL_GPL(percpu_depopulate);
if (!pdata)
/**
* 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
*/
void __percpu_depopulate_mask(void *__pdata, cpumask_t *mask)
{
int cpu;
for_each_cpu_mask(cpu, *mask)
percpu_depopulate(__pdata, cpu);
}
EXPORT_SYMBOL_GPL(__percpu_depopulate_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.
*/
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);
BUG_ON(pdata->ptrs[cpu]);
if (node_online(node)) {
/* FIXME: kzalloc_node(size, gfp, node) */
pdata->ptrs[cpu] = kmalloc_node(size, gfp, node);
if (pdata->ptrs[cpu])
memset(pdata->ptrs[cpu], 0, size);
} else
pdata->ptrs[cpu] = kzalloc(size, gfp);
return pdata->ptrs[cpu];
}
EXPORT_SYMBOL_GPL(percpu_populate);
/**
* 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.
*/
int __percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
cpumask_t *mask)
{
cpumask_t populated = CPU_MASK_NONE;
int cpu;
for_each_cpu_mask(cpu, *mask)
if (unlikely(!percpu_populate(__pdata, size, gfp, cpu))) {
__percpu_depopulate_mask(__pdata, &populated);
return -ENOMEM;
} else
cpu_set(cpu, populated);
return 0;
}
EXPORT_SYMBOL_GPL(__percpu_populate_mask);
/**
* percpu_alloc_mask - initial setup of per-cpu data
* @size: size of per-cpu object
* @gfp: may sleep or not etc.
* @mask: populate per-data for cpu's selected through mask bits
*
* Populating per-cpu data for all online cpu's would be a typical use case,
* which is simplified by the percpu_alloc() wrapper.
* Per-cpu objects are populated with zeroed buffers.
*/
void *__percpu_alloc_mask(size_t size, gfp_t gfp, cpumask_t *mask)
{
void *pdata = kzalloc(sizeof(struct percpu_data), gfp);
void *__pdata = __percpu_disguise(pdata);
if (unlikely(!pdata))
return NULL;
/*
* Cannot use for_each_online_cpu since a cpu may come online
* and we have no way of figuring out how to fix the array
* that we have allocated then....
*/
for_each_possible_cpu(i) {
int node = cpu_to_node(i);
if (node_online(node))
pdata->ptrs[i] = kmalloc_node(size, GFP_KERNEL, node);
else
pdata->ptrs[i] = kmalloc(size, GFP_KERNEL);
if (!pdata->ptrs[i])
goto unwind_oom;
memset(pdata->ptrs[i], 0, size);
}
/* Catch derefs w/o wrappers */
return (void *)(~(unsigned long)pdata);
unwind_oom:
while (--i >= 0) {
if (!cpu_possible(i))
continue;
kfree(pdata->ptrs[i]);
}
if (likely(!__percpu_populate_mask(__pdata, size, gfp, mask)))
return __pdata;
kfree(pdata);
return NULL;
}
EXPORT_SYMBOL(__alloc_percpu);
#endif
EXPORT_SYMBOL_GPL(__percpu_alloc_mask);
/**
* percpu_free - 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 percpu_free(void *__pdata)
{
__percpu_depopulate_mask(__pdata, &cpu_possible_map);
kfree(__percpu_disguise(__pdata));
}
EXPORT_SYMBOL_GPL(percpu_free);
#endif /* CONFIG_SMP */
/**
* kmem_cache_free - Deallocate an object
@ -3463,29 +3538,6 @@ void kfree(const void *objp)
}
EXPORT_SYMBOL(kfree);
#ifdef CONFIG_SMP
/**
* free_percpu - free previously allocated percpu memory
* @objp: pointer returned by alloc_percpu.
*
* Don't free memory not originally allocated by alloc_percpu()
* The complemented objp is to check for that.
*/
void free_percpu(const void *objp)
{
int i;
struct percpu_data *p = (struct percpu_data *)(~(unsigned long)objp);
/*
* We allocate for all cpus so we cannot use for online cpu here.
*/
for_each_possible_cpu(i)
kfree(p->ptrs[i]);
kfree(p);
}
EXPORT_SYMBOL(free_percpu);
#endif
unsigned int kmem_cache_size(struct kmem_cache *cachep)
{
return obj_size(cachep);