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 <[email protected]>
---
include/linux/percpu.h | 74 ++++++++++++++++-----
mm/slab.c | 165 ++++++++++++++++++++++++++++++++-----------------
2 files changed, 162 insertions(+), 77 deletions(-)
diff -ur a/include/linux/percpu.h b/include/linux/percpu.h
--- a/include/linux/percpu.h 2006-06-18 03:49:35.000000000 +0200
+++ b/include/linux/percpu.h 2006-07-24 15:13:36.000000000 +0200
@@ -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. */
@@ -21,39 +24,70 @@
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 map);
+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 percpu_depopulate(void *__pdata, int cpu)
+{
+}
+
+static inline void percpu_depopulate_mask(void *__pdata, cpumask_t mask)
+{
+}
-static inline void *__alloc_percpu(size_t size)
+static inline void *percpu_populate(void *__pdata, size_t size, gfp_t gfp,
+ 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);
+ return percpu_ptr(__pdata, cpu);
+}
+
+static inline int percpu_populate_mask(void *__pdata, size_t size, gfp_t gfp,
+ int cpu)
+{
+ return 0;
+}
+
+static inline void *percpu_alloc_mask(size_t size, gfp_t gfp, cpumask_t map)
+{
+ 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_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 */
diff -ur a/mm/slab.c b/mm/slab.c
--- a/mm/slab.c 2006-07-24 15:11:58.000000000 +0200
+++ b/mm/slab.c 2006-07-24 15:13:36.000000000 +0200
@@ -3374,52 +3374,126 @@
#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)
- return 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
+ */
+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);
- /*
- * 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);
+/**
+ * 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);
- if (node_online(node))
- pdata->ptrs[i] = kmalloc_node(size, GFP_KERNEL, node);
- else
- pdata->ptrs[i] = kmalloc(size, GFP_KERNEL);
+ 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);
- if (!pdata->ptrs[i])
- goto unwind_oom;
- memset(pdata->ptrs[i], 0, size);
- }
+/**
+ * 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;
- /* Catch derefs w/o wrappers */
- return (void *)(~(unsigned long)pdata);
+ 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);
-unwind_oom:
- while (--i >= 0) {
- if (!cpu_possible(i))
- continue;
- kfree(pdata->ptrs[i]);
- }
+/**
+ * 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;
+ 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
@@ -3466,29 +3540,6 @@
}
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);
-
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