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Subject[patch] kmalloc_percpu
Here's  kmalloc_percpu interfaces ported (...mostly rediffed) to 
2.5.45. (One last try for 2.6). I guess we can use
DECLARE_PER_CPU interfaces most of the places; But for per_cpu stuff
which could possibly be defined in modules, kmalloc_percpu might be useful
(SNMP stats for ex...ipv6 can be compiled as a module).

-Kiran

Name: kmalloc_percpu
Description: Dynamic percpu allocator
Author: Dipankar Sarma & Ravikiran Thirumalai

diff -X dontdiff -ruN linux-2.5.45/include/linux/slab.h kmalloc_percpu-2.5.45/include/linux/slab.h
--- linux-2.5.45/include/linux/slab.h Thu Oct 31 06:13:45 2002
+++ kmalloc_percpu-2.5.45/include/linux/slab.h Thu Oct 31 18:26:24 2002
@@ -13,6 +13,7 @@

#include <linux/gfp.h>
#include <linux/types.h>
+#include <linux/smp.h>

/* flags for kmem_cache_alloc() */
#define SLAB_NOFS GFP_NOFS
@@ -63,6 +64,42 @@

extern int FASTCALL(kmem_cache_reap(int));

+#ifdef CONFIG_SMP
+
+struct percpu_data {
+ void *ptrs[NR_CPUS];
+ void *blkp;
+};
+
+#define per_cpu_ptr(ptr, cpu) \
+({ \
+ struct percpu_data *__p = (struct percpu_data *)~(unsigned long)(ptr); \
+ (__typeof__(ptr))__p->ptrs[(cpu)]; \
+})
+#define this_cpu_ptr(ptr) per_cpu_ptr(ptr, smp_processor_id())
+extern void *kmalloc_percpu(size_t size, int flags);
+extern void kfree_percpu(const void *);
+extern int percpu_interlaced_alloc(struct percpu_data *, size_t, int);
+extern void percpu_interlaced_free(struct percpu_data *);
+extern void percpu_data_sys_init(void);
+
+#else
+
+#define per_cpu_ptr(ptr, cpu) (ptr)
+#define this_cpu_ptr(ptr) (ptr)
+static inline void *kmalloc_percpu(size_t size, int flags)
+{
+ return(kmalloc(size, flags));
+}
+static inline void kfree_percpu(const void *ptr)
+{
+ kfree(ptr);
+}
+static inline void percpu_data_sys_init(void) { }
+
+#endif
+
+
/* System wide caches */
extern kmem_cache_t *vm_area_cachep;
extern kmem_cache_t *mm_cachep;
diff -X dontdiff -ruN linux-2.5.45/init/main.c kmalloc_percpu-2.5.45/init/main.c
--- linux-2.5.45/init/main.c Thu Oct 31 06:11:58 2002
+++ kmalloc_percpu-2.5.45/init/main.c Thu Oct 31 17:48:09 2002
@@ -423,6 +423,7 @@
page_address_init();
mem_init();
kmem_cache_sizes_init();
+ percpu_data_sys_init();
pidhash_init();
pgtable_cache_init();
pte_chain_init();
diff -X dontdiff -ruN linux-2.5.45/kernel/ksyms.c kmalloc_percpu-2.5.45/kernel/ksyms.c
--- linux-2.5.45/kernel/ksyms.c Thu Oct 31 06:11:34 2002
+++ kmalloc_percpu-2.5.45/kernel/ksyms.c Thu Oct 31 17:48:09 2002
@@ -104,6 +104,10 @@
EXPORT_SYMBOL(remove_shrinker);
EXPORT_SYMBOL(kmalloc);
EXPORT_SYMBOL(kfree);
+#ifdef CONFIG_SMP
+EXPORT_SYMBOL(kmalloc_percpu);
+EXPORT_SYMBOL(kfree_percpu);
+#endif
EXPORT_SYMBOL(vfree);
EXPORT_SYMBOL(__vmalloc);
EXPORT_SYMBOL(vmalloc);
diff -X dontdiff -ruN linux-2.5.45/mm/Makefile kmalloc_percpu-2.5.45/mm/Makefile
--- linux-2.5.45/mm/Makefile Thu Oct 31 06:13:03 2002
+++ kmalloc_percpu-2.5.45/mm/Makefile Thu Oct 31 17:52:55 2002
@@ -2,7 +2,8 @@
# Makefile for the linux memory manager.
#

-export-objs := shmem.o filemap.o mempool.o page_alloc.o page-writeback.o
+export-objs := shmem.o filemap.o mempool.o page_alloc.o page-writeback.o \
+ percpu_data.o

obj-y := memory.o mmap.o filemap.o mprotect.o mlock.o mremap.o \
vmalloc.o slab.o bootmem.o swap.o vmscan.o page_io.o \
@@ -11,4 +12,5 @@
pdflush.o page-writeback.o rmap.o madvise.o vcache.o \
truncate.o

+obj-$(CONFIG_SMP) += percpu_data.o
include $(TOPDIR)/Rules.make
diff -X dontdiff -ruN linux-2.5.45/mm/percpu_data.c kmalloc_percpu-2.5.45/mm/percpu_data.c
--- linux-2.5.45/mm/percpu_data.c Thu Jan 1 05:30:00 1970
+++ kmalloc_percpu-2.5.45/mm/percpu_data.c Thu Oct 31 17:48:09 2002
@@ -0,0 +1,376 @@
+/*
+ * Dynamic Per-CPU Data Allocator.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (c) IBM Corporation, 2002
+ *
+ * Author: Dipankar Sarma <dipankar@in.ibm.com>
+ * Ravikiran G. Thirumalai <kiran@in.ibm.com>
+ *
+ */
+
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cache.h>
+
+struct percpu_data_blklist {
+ struct list_head blks;
+ struct list_head *firstnotfull;
+ spinlock_t lock;
+ size_t objsize;
+ size_t blksize;
+ kmem_cache_t *cachep;
+ char *cachename;
+};
+
+struct percpu_data_blk {
+ struct list_head linkage;
+ void *blkaddr[NR_CPUS];
+ unsigned int usecount;
+ int *freearr;
+ int freehead;
+ struct percpu_data_blklist *blklist;
+};
+
+static struct percpu_data_blklist data_blklist[] = {
+ {
+ .blks = LIST_HEAD_INIT(data_blklist[0].blks),
+ .firstnotfull = &data_blklist[0].blks,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .objsize = 4,
+ .blksize = ((4 + SMP_CACHE_BYTES - 1) & ~(SMP_CACHE_BYTES - 1)),
+ .cachep = NULL,
+ .cachename = "percpu_data_4"
+ },
+ {
+ .blks = LIST_HEAD_INIT(data_blklist[1].blks),
+ .firstnotfull = &data_blklist[1].blks,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .objsize = 8,
+ .blksize = ((8 + SMP_CACHE_BYTES - 1) & ~(SMP_CACHE_BYTES - 1)),
+ .cachep = NULL,
+ .cachename = "percpu_data_8"
+ },
+ {
+ .blks = LIST_HEAD_INIT(data_blklist[2].blks),
+ .firstnotfull = &data_blklist[2].blks,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .objsize = 16,
+ .blksize = ((16 + SMP_CACHE_BYTES - 1) &
+ ~(SMP_CACHE_BYTES - 1)),
+ .cachep = NULL,
+ .cachename = "percpu_data_16"
+ },
+#if PAGE_SIZE != 4096
+ {
+ .blks = LIST_HEAD_INIT(data_blklist[3].blks),
+ .firstnotfull = &data_blklist[3].blks,
+ .lock = SPIN_LOCK_UNLOCKED,
+ .objsize = 32,
+ .blksize = ((32 + SMP_CACHE_BYTES - 1) &
+ ~(SMP_CACHE_BYTES - 1)),
+ .cachep = NULL,
+ .cachename = "percpu_data_32"
+ }
+#endif
+};
+
+static int data_blklist_count =
+ sizeof(data_blklist)/sizeof(struct percpu_data_blklist);
+
+/*
+ * Allocate a block descriptor structure and initialize it.
+ * Returns the address of the block descriptor or NULL on failure.
+ */
+static struct percpu_data_blk *percpu_data_blk_alloc(
+ struct percpu_data_blklist *blklist, int flags)
+{
+ struct percpu_data_blk *blkp;
+ int i;
+ int count;
+
+ if (!(blkp = kmalloc(sizeof(struct percpu_data_blk), flags)))
+ goto out1;
+ INIT_LIST_HEAD(&blkp->linkage);
+ blkp->usecount = 0;
+ count = blklist->blksize / blklist->objsize;
+ blkp->freearr = kmalloc(count, flags);
+ if (!blkp->freearr)
+ goto out;
+ blkp->freehead = 0;
+ for (i = 0; i < count; i++)
+ blkp->freearr[i] = i+1;
+ blkp->freearr[i-1] = -1; /* Marks the end of the array */
+ blkp->blklist = blklist;
+ return blkp;
+out:
+ kfree(blkp);
+out1:
+ return NULL;
+}
+
+/*
+ * Frees the block descriptor structure
+ */
+static void percpu_data_blk_free(struct percpu_data_blk *blkp)
+{
+ kfree(blkp);
+}
+
+/*
+ * Add a block to the percpu data object memory pool.
+ * Returns 0 on failure and 1 on success
+ */
+static int percpu_data_mem_grow(struct percpu_data_blklist *blklist, int flags)
+{
+ struct percpu_data_blk *blkp;
+ unsigned long save_flags;
+ int i;
+
+ if (!(blkp = percpu_data_blk_alloc(blklist, flags)))
+ goto out;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_possible(i))
+ continue;
+ blkp->blkaddr[i] = kmem_cache_alloc(blklist->cachep, flags);
+ if(!(blkp->blkaddr[i]))
+ goto out1;
+ memset(blkp->blkaddr[i], 0, blklist->blksize);
+ }
+
+ /*
+ * Now that we have the block successfully allocated
+ * and instantiated.. add it.....
+ */
+ spin_lock_irqsave(&blklist->lock, save_flags);
+ list_add_tail(&blkp->linkage, &blklist->blks);
+ if (blklist->firstnotfull == &blklist->blks)
+ blklist->firstnotfull = &blkp->linkage;
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ return 1;
+
+out1:
+ i--;
+ for (; i >= 0; i--) {
+ if (!cpu_possible(i))
+ continue;
+ kmem_cache_free(blklist->cachep, blkp->blkaddr[i]);
+ }
+ percpu_data_blk_free(blkp);
+out:
+ return 0;
+}
+
+/*
+ * Initialise the main percpu data control structure.
+ */
+static void percpu_data_blklist_init(struct percpu_data_blklist *blklist)
+{
+ blklist->cachep = kmem_cache_create(blklist->cachename,
+ blklist->blksize, 0, SLAB_HWCACHE_ALIGN,
+ NULL, NULL);
+ if(!blklist->cachep)
+ BUG();
+}
+
+
+static struct percpu_data_blklist *percpu_data_get_blklist(size_t size,
+ int flags)
+{
+ int i;
+ for (i = 0; i < data_blklist_count; i++) {
+ if (size > data_blklist[i].objsize)
+ continue;
+ return &data_blklist[i];
+ }
+ return NULL;
+}
+
+
+/*
+ * Initialize the percpu_data subsystem.
+ */
+void __init percpu_data_sys_init(void)
+{
+ int i;
+ for (i = 0; i < data_blklist_count; i++) {
+ percpu_data_blklist_init(&data_blklist[i]);
+ }
+}
+
+/*
+ * Allocs an object from the block. Returns back the object index.
+ */
+static int __percpu_interlaced_alloc_one(struct percpu_data_blklist *blklist,
+ struct percpu_data_blk *blkp)
+{
+ unsigned int objidx;
+
+ objidx = blkp->freehead;
+ blkp->freehead = blkp->freearr[objidx];
+ blkp->usecount++;
+ if(blkp->freehead < 0) {
+ blklist->firstnotfull = blkp->linkage.next;
+ }
+ return objidx;
+}
+
+/*
+ * Allocate a per cpu data object and return a pointer to it.
+ */
+static int __percpu_interlaced_alloc(struct percpu_data *percpu,
+ struct percpu_data_blklist *blklist, int flags)
+{
+ struct percpu_data_blk *blkp;
+ unsigned long save_flags;
+ struct list_head *l;
+ int objidx;
+ int i;
+
+tryagain:
+
+ spin_lock_irqsave(&blklist->lock, save_flags);
+ l = blklist->firstnotfull;
+ if (l == &blklist->blks)
+ goto unlock_and_get_mem;
+ blkp = list_entry(l, struct percpu_data_blk, linkage);
+
+ objidx = __percpu_interlaced_alloc_one(blklist, blkp);
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ /*
+ * Since we hold the lock and firstnotfull is not the
+ * head list, we should be getting an object alloc here. firstnotfull
+ * can be pointing to head of the list when all the blks are
+ * full or when there're no blocks left
+ */
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_possible(i))
+ continue;
+ percpu->ptrs[i] = blkp->blkaddr[i] + objidx * blklist->objsize;
+ }
+ percpu->blkp = (void *)blkp;
+ return 1;
+
+unlock_and_get_mem:
+
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ if(percpu_data_mem_grow(blklist, flags))
+ goto tryagain; /* added another block..try allocing obj ..*/
+
+ return 0;
+}
+
+/*
+ * Allocate a per-cpu data object and return a pointer to it.
+ * Returns NULL on failure.
+ */
+int percpu_interlaced_alloc(struct percpu_data *pdata, size_t size, int flags)
+{
+ struct percpu_data_blklist *blklist;
+
+ blklist = percpu_data_get_blklist(size, flags);
+ if (blklist == NULL)
+ return 0;
+ return __percpu_interlaced_alloc(pdata, blklist, flags);
+}
+
+/*
+ * Frees memory associated with a percpu data block
+ */
+static void percpu_data_blk_destroy(struct percpu_data_blklist *blklist,
+ struct percpu_data_blk *blkp)
+{
+ int i;
+
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_possible(i))
+ continue;
+ kmem_cache_free(blklist->cachep, blkp->blkaddr[i]);
+ }
+ percpu_data_blk_free(blkp);
+}
+
+/*
+ * Frees an object from a block and fixes the freelist accdly.
+ * Frees the slab cache memory if a block gets empty during free.
+ */
+static void __percpu_interlaced_free(struct percpu_data_blklist *blklist,
+ struct percpu_data *percpu)
+{
+ struct percpu_data_blk *blkp;
+ int objidx;
+ int objoffset;
+ struct list_head *t;
+ unsigned long save_flags;
+
+ spin_lock_irqsave(&blklist->lock, save_flags);
+ blkp = (struct percpu_data_blk *)percpu->blkp;
+ objoffset = percpu->ptrs[0] - blkp->blkaddr[0];
+ objidx = objoffset / blklist->objsize;
+
+ kfree(percpu);
+
+ blkp->freearr[objidx] = blkp->freehead;
+ blkp->freehead = objidx;
+ blkp->usecount--;
+
+ if (blkp->freearr[objidx] < 0) {
+ /*
+ * block was previously full and is now just partially full ..
+ * so make firstnotfull pt to this block and fix list accdly
+ */
+ t = blklist->firstnotfull;
+ blklist->firstnotfull = &blkp->linkage;
+ if (blkp->linkage.next == t) {
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ return;
+ }
+ list_del(&blkp->linkage);
+ list_add_tail(&blkp->linkage, t);
+
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ return;
+ }
+
+ if (blkp->usecount == 0) {
+ t = blklist->firstnotfull->prev;
+
+ list_del(&blkp->linkage);
+ if (blklist->firstnotfull == &blkp->linkage)
+ blklist->firstnotfull = t->next;
+
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ percpu_data_blk_destroy(blklist, blkp);
+ return;
+ }
+
+ spin_unlock_irqrestore(&blklist->lock, save_flags);
+ return;
+}
+
+/*
+ * Frees up a percpu data object
+ */
+void percpu_interlaced_free(struct percpu_data *percpu)
+{
+ struct percpu_data_blk *blkp = percpu->blkp;
+ __percpu_interlaced_free(blkp->blklist, percpu);
+}
diff -X dontdiff -ruN linux-2.5.45/mm/slab.c kmalloc_percpu-2.5.45/mm/slab.c
--- linux-2.5.45/mm/slab.c Thu Oct 31 06:13:36 2002
+++ kmalloc_percpu-2.5.45/mm/slab.c Thu Oct 31 18:44:11 2002
@@ -1824,6 +1824,58 @@
return NULL;
}

+#ifdef CONFIG_SMP
+/**
+ * kmalloc_percpu - allocate one copy of the object for every present
+ * cpu in the system.
+ *
+ * @size: how many bytes of memory are required.
+ * @flags: the type of memory to allocate.
+ * The @flags argument may be one of:
+ *
+ * %GFP_USER - Allocate memory on behalf of user. May sleep.
+ *
+ * %GFP_KERNEL - Allocate normal kernel ram. May sleep.
+ *
+ * %GFP_ATOMIC - Allocation will not sleep. Use inside interrupt handlers.
+ */
+void *kmalloc_percpu(size_t size, int flags)
+{
+ int i;
+ struct percpu_data *pdata = kmalloc(sizeof(*pdata), flags);
+
+ if (!pdata)
+ goto out_done;
+ pdata->blkp = NULL;
+ if (size <= (malloc_sizes[0].cs_size << 1)) {
+ if (!percpu_interlaced_alloc(pdata, size, flags))
+ goto out;
+ } else {
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_possible(i))
+ continue;
+ pdata->ptrs[i] = kmalloc(size, flags);
+ if (!pdata->ptrs[i])
+ goto unwind_oom;
+ }
+ }
+ /* Catch derefs w/o wrappers */
+ return (void *)(~(unsigned long)pdata);
+
+unwind_oom:
+ while (--i >= 0) {
+ if (!cpu_possible(i))
+ continue;
+ kfree(pdata->ptrs[i]);
+ }
+out:
+ kfree(pdata);
+out_done:
+ return NULL;
+}
+#endif
+
+
/**
* kmem_cache_free - Deallocate an object
* @cachep: The cache the allocation was from.
@@ -1871,6 +1923,32 @@
return cachep->objsize;
}

+#ifdef CONFIG_SMP
+/**
+ * kfree_percpu - free previously allocated percpu memory
+ * @objp: pointer returned by kmalloc_percpu.
+ *
+ * Don't free memory not originally allocated by kmalloc_percpu()
+ * The complemented objp is to check for that.
+ */
+void kfree_percpu(const void *objp)
+{
+ int i;
+ struct percpu_data *p = (struct percpu_data *)(~(unsigned long)objp);
+
+ if (p->blkp) {
+ percpu_interlaced_free(p);
+ } else {
+ for (i = 0; i < NR_CPUS; i++) {
+ if (!cpu_possible(i))
+ continue;
+ kfree(p->ptrs[i]);
+ }
+ }
+}
+#endif
+
+
kmem_cache_t * kmem_find_general_cachep (size_t size, int gfpflags)
{
struct cache_sizes *csizep = malloc_sizes;
-
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