Hello, Seth. Here comes minor comments. On Wed, Feb 20, 2013 at 04:04:44PM -0600, Seth Jennings wrote: > zswap is a thin compression backend for frontswap. It receives > pages from frontswap and attempts to store them in a compressed > memory pool, resulting in an effective partial memory reclaim and > dramatically reduced swap device I/O. > > Additionally, in most cases, pages can be retrieved from this > compressed store much more quickly than reading from tradition > swap devices resulting in faster performance for many workloads. > > This patch adds the zswap driver to mm/ > > Signed-off-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> > --- > mm/Kconfig | 15 ++ > mm/Makefile | 1 + > mm/zswap.c | 665 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 681 insertions(+) > create mode 100644 mm/zswap.c > > diff --git a/mm/Kconfig b/mm/Kconfig > index 25b8f38..f9f35b7 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -470,3 +470,18 @@ config PGTABLE_MAPPING > > You can check speed with zsmalloc benchmark[1]. > [1] https://github.com/spartacus06/zsmalloc > + > +config ZSWAP > + bool "In-kernel swap page compression" > + depends on FRONTSWAP && CRYPTO > + select CRYPTO_LZO > + select ZSMALLOC > + default n > + help > + Zswap is a backend for the frontswap mechanism in the VMM. > + It receives pages from frontswap and attempts to store them > + in a compressed memory pool, resulting in an effective > + partial memory reclaim. In addition, pages and be retrieved > + from this compressed store much faster than most tradition > + swap devices resulting in reduced I/O and faster performance > + for many workloads. > diff --git a/mm/Makefile b/mm/Makefile > index 0f6ef0a..1e0198f 100644 > --- a/mm/Makefile > +++ b/mm/Makefile > @@ -32,6 +32,7 @@ obj-$(CONFIG_HAVE_MEMBLOCK) += memblock.o > obj-$(CONFIG_BOUNCE) += bounce.o > obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o > obj-$(CONFIG_FRONTSWAP) += frontswap.o > +obj-$(CONFIG_ZSWAP) += zswap.o > obj-$(CONFIG_HAS_DMA) += dmapool.o > obj-$(CONFIG_HUGETLBFS) += hugetlb.o > obj-$(CONFIG_NUMA) += mempolicy.o > diff --git a/mm/zswap.c b/mm/zswap.c > new file mode 100644 > index 0000000..d3b4943 > --- /dev/null > +++ b/mm/zswap.c > @@ -0,0 +1,665 @@ > +/* > + * zswap.c - zswap driver file > + * > + * zswap is a backend for frontswap that takes pages that are in the > + * process of being swapped out and attempts to compress them and store > + * them in a RAM-based memory pool. This results in a significant I/O > + * reduction on the real swap device and, in the case of a slow swap > + * device, can also improve workload performance. > + * > + * Copyright (C) 2012 Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> > + * > + * 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. > +*/ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > + > +#include <linux/module.h> > +#include <linux/cpu.h> > +#include <linux/highmem.h> > +#include <linux/slab.h> > +#include <linux/spinlock.h> > +#include <linux/types.h> > +#include <linux/atomic.h> > +#include <linux/frontswap.h> > +#include <linux/rbtree.h> > +#include <linux/swap.h> > +#include <linux/crypto.h> > +#include <linux/mempool.h> > +#include <linux/zsmalloc.h> > + > +/********************************* > +* statistics > +**********************************/ > +/* Number of memory pages used by the compressed pool */ > +static atomic_t zswap_pool_pages = ATOMIC_INIT(0); > +/* The number of compressed pages currently stored in zswap */ > +static atomic_t zswap_stored_pages = ATOMIC_INIT(0); > + > +/* > + * The statistics below are not protected from concurrent access for > + * performance reasons so they may not be a 100% accurate. However, > + * they do provide useful information on roughly how many times a > + * certain event is occurring. > +*/ > +static u64 zswap_pool_limit_hit; > +static u64 zswap_reject_compress_poor; > +static u64 zswap_reject_zsmalloc_fail; > +static u64 zswap_reject_kmemcache_fail; > +static u64 zswap_duplicate_entry; > + > +/********************************* > +* tunables > +**********************************/ > +/* Enable/disable zswap (disabled by default, fixed at boot for now) */ > +static bool zswap_enabled; > +module_param_named(enabled, zswap_enabled, bool, 0); > + > +/* Compressor to be used by zswap (fixed at boot for now) */ > +#define ZSWAP_COMPRESSOR_DEFAULT "lzo" > +static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; > +module_param_named(compressor, zswap_compressor, charp, 0); > + > +/* The maximum percentage of memory that the compressed pool can occupy */ > +static unsigned int zswap_max_pool_percent = 20; > +module_param_named(max_pool_percent, > + zswap_max_pool_percent, uint, 0644); > + > +/* > + * Maximum compression ratio, as as percentage, for an acceptable > + * compressed page. Any pages that do not compress by at least > + * this ratio will be rejected. > +*/ > +static unsigned int zswap_max_compression_ratio = 80; > +module_param_named(max_compression_ratio, > + zswap_max_compression_ratio, uint, 0644); > + > +/********************************* > +* compression functions > +**********************************/ > +/* per-cpu compression transforms */ > +static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms; > + > +enum comp_op { > + ZSWAP_COMPOP_COMPRESS, > + ZSWAP_COMPOP_DECOMPRESS > +}; > + > +static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen, > + u8 *dst, unsigned int *dlen) > +{ > + struct crypto_comp *tfm; > + int ret; > + > + tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu()); > + switch (op) { > + case ZSWAP_COMPOP_COMPRESS: > + ret = crypto_comp_compress(tfm, src, slen, dst, dlen); > + break; > + case ZSWAP_COMPOP_DECOMPRESS: > + ret = crypto_comp_decompress(tfm, src, slen, dst, dlen); > + break; > + default: > + ret = -EINVAL; > + } > + > + put_cpu(); > + return ret; > +} > + > +static int __init zswap_comp_init(void) > +{ > + if (!crypto_has_comp(zswap_compressor, 0, 0)) { > + pr_info("%s compressor not available\n", zswap_compressor); > + /* fall back to default compressor */ > + zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; > + if (!crypto_has_comp(zswap_compressor, 0, 0)) > + /* can't even load the default compressor */ > + return -ENODEV; > + } > + pr_info("using %s compressor\n", zswap_compressor); > + > + /* alloc percpu transforms */ > + zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *); > + if (!zswap_comp_pcpu_tfms) > + return -ENOMEM; > + return 0; > +} > + > +static void zswap_comp_exit(void) > +{ > + /* free percpu transforms */ > + if (zswap_comp_pcpu_tfms) > + free_percpu(zswap_comp_pcpu_tfms); > +} > + > +/********************************* > +* data structures > +**********************************/ > +struct zswap_entry { > + struct rb_node rbnode; > + unsigned type; > + pgoff_t offset; > + unsigned long handle; > + unsigned int length; > +}; > + > +struct zswap_tree { > + struct rb_root rbroot; > + spinlock_t lock; > + struct zs_pool *pool; > +}; > + > +static struct zswap_tree *zswap_trees[MAX_SWAPFILES]; > + > +/********************************* > +* zswap entry functions > +**********************************/ > +#define ZSWAP_KMEM_CACHE_NAME "zswap_entry_cache" > +static struct kmem_cache *zswap_entry_cache; > + > +static inline int zswap_entry_cache_create(void) > +{ > + zswap_entry_cache = > + kmem_cache_create(ZSWAP_KMEM_CACHE_NAME, > + sizeof(struct zswap_entry), 0, 0, NULL); > + return (zswap_entry_cache == NULL); > +} > + > +static inline void zswap_entry_cache_destory(void) > +{ > + kmem_cache_destroy(zswap_entry_cache); > +} > + > +static inline struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp) > +{ > + struct zswap_entry *entry; > + entry = kmem_cache_alloc(zswap_entry_cache, gfp); > + if (!entry) > + return NULL; > + return entry; > +} > + > +static inline void zswap_entry_cache_free(struct zswap_entry *entry) > +{ > + kmem_cache_free(zswap_entry_cache, entry); > +} > + > +/********************************* > +* rbtree functions > +**********************************/ > +static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset) > +{ > + struct rb_node *node = root->rb_node; > + struct zswap_entry *entry; > + > + while (node) { > + entry = rb_entry(node, struct zswap_entry, rbnode); > + if (entry->offset > offset) > + node = node->rb_left; > + else if (entry->offset < offset) > + node = node->rb_right; > + else > + return entry; > + } > + return NULL; > +} > + > +/* > + * In the case that a entry with the same offset is found, it a pointer to > + * the existing entry is stored in dupentry and the function returns -EEXIST > +*/ > +static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry, > + struct zswap_entry **dupentry) > +{ > + struct rb_node **link = &root->rb_node, *parent = NULL; > + struct zswap_entry *myentry; > + > + while (*link) { > + parent = *link; > + myentry = rb_entry(parent, struct zswap_entry, rbnode); > + if (myentry->offset > entry->offset) > + link = &(*link)->rb_left; > + else if (myentry->offset < entry->offset) > + link = &(*link)->rb_right; > + else { > + *dupentry = myentry; > + return -EEXIST; > + } > + } > + rb_link_node(&entry->rbnode, parent, link); > + rb_insert_color(&entry->rbnode, root); > + return 0; > +} > + > +/********************************* > +* per-cpu code > +**********************************/ > +static DEFINE_PER_CPU(u8 *, zswap_dstmem); > + > +static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu) > +{ > + struct crypto_comp *tfm; > + u8 *dst; > + > + switch (action) { > + case CPU_UP_PREPARE: > + tfm = crypto_alloc_comp(zswap_compressor, 0, 0); > + if (IS_ERR(tfm)) { > + pr_err("can't allocate compressor transform\n"); > + return NOTIFY_BAD; > + } > + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm; > + dst = (u8 *)__get_free_pages(GFP_KERNEL, 1); Order 1 is really needed? Following code uses only PAGE_SIZE, not 2 * PAGE_SIZE. > + if (!dst) { > + pr_err("can't allocate compressor buffer\n"); > + crypto_free_comp(tfm); > + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL; > + return NOTIFY_BAD; > + } > + per_cpu(zswap_dstmem, cpu) = dst; > + break; > + case CPU_DEAD: > + case CPU_UP_CANCELED: > + tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu); > + if (tfm) { > + crypto_free_comp(tfm); > + *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL; > + } > + dst = per_cpu(zswap_dstmem, cpu); > + if (dst) { > + free_pages((unsigned long)dst, 1); > + per_cpu(zswap_dstmem, cpu) = NULL; > + } > + break; > + default: > + break; > + } > + return NOTIFY_OK; > +} > + > +static int zswap_cpu_notifier(struct notifier_block *nb, > + unsigned long action, void *pcpu) > +{ > + unsigned long cpu = (unsigned long)pcpu; > + return __zswap_cpu_notifier(action, cpu); > +} > + > +static struct notifier_block zswap_cpu_notifier_block = { > + .notifier_call = zswap_cpu_notifier > +}; > + > +static int zswap_cpu_init(void) > +{ > + unsigned long cpu; > + > + get_online_cpus(); > + for_each_online_cpu(cpu) > + if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK) > + goto cleanup; > + register_cpu_notifier(&zswap_cpu_notifier_block); > + put_online_cpus(); > + return 0; > + > +cleanup: > + for_each_online_cpu(cpu) > + __zswap_cpu_notifier(CPU_UP_CANCELED, cpu); > + put_online_cpus(); > + return -ENOMEM; > +} > + > +/********************************* > +* zsmalloc callbacks > +**********************************/ > +static mempool_t *zswap_page_pool; > + > +static inline unsigned int zswap_max_pool_pages(void) > +{ > + return zswap_max_pool_percent * totalram_pages / 100; > +} > + > +static inline int zswap_page_pool_create(void) > +{ > + /* TODO: dynamically size mempool */ > + zswap_page_pool = mempool_create_page_pool(256, 0); > + if (!zswap_page_pool) > + return -ENOMEM; > + return 0; > +} > + > +static inline void zswap_page_pool_destroy(void) > +{ > + mempool_destroy(zswap_page_pool); > +} > + > +static struct page *zswap_alloc_page(gfp_t flags) > +{ > + struct page *page; > + > + if (atomic_read(&zswap_pool_pages) >= zswap_max_pool_pages()) { > + zswap_pool_limit_hit++; > + return NULL; > + } > + page = mempool_alloc(zswap_page_pool, flags); > + if (page) > + atomic_inc(&zswap_pool_pages); > + return page; > +} > + > +static void zswap_free_page(struct page *page) > +{ > + if (!page) > + return; > + mempool_free(page, zswap_page_pool); > + atomic_dec(&zswap_pool_pages); > +} > + > +static struct zs_ops zswap_zs_ops = { > + .alloc = zswap_alloc_page, > + .free = zswap_free_page > +}; > + > +/********************************* > +* frontswap hooks > +**********************************/ > +/* attempts to compress and store an single page */ > +static int zswap_frontswap_store(unsigned type, pgoff_t offset, > + struct page *page) > +{ > + struct zswap_tree *tree = zswap_trees[type]; > + struct zswap_entry *entry, *dupentry; > + int ret; > + unsigned int dlen = PAGE_SIZE; > + unsigned long handle; > + char *buf; > + u8 *src, *dst; > + > + if (!tree) { > + ret = -ENODEV; > + goto reject; > + } > + > + /* compress */ > + dst = get_cpu_var(zswap_dstmem); > + src = kmap_atomic(page); > + ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen); > + kunmap_atomic(src); > + if (ret) { > + ret = -EINVAL; > + goto putcpu; > + } > + if ((dlen * 100 / PAGE_SIZE) > zswap_max_compression_ratio) { > + zswap_reject_compress_poor++; > + ret = -E2BIG; > + goto putcpu; > + } > + > + /* store */ > + handle = zs_malloc(tree->pool, dlen, > + __GFP_NORETRY | __GFP_HIGHMEM | __GFP_NOMEMALLOC | > + __GFP_NOWARN); > + if (!handle) { > + zswap_reject_zsmalloc_fail++; > + ret = -ENOMEM; > + goto putcpu; > + } > + > + buf = zs_map_object(tree->pool, handle, ZS_MM_WO); > + memcpy(buf, dst, dlen); > + zs_unmap_object(tree->pool, handle); > + put_cpu_var(zswap_dstmem); > + > + /* allocate entry */ > + entry = zswap_entry_cache_alloc(GFP_KERNEL); > + if (!entry) { > + zs_free(tree->pool, handle); > + zswap_reject_kmemcache_fail++; > + ret = -ENOMEM; > + goto reject; > + } How about moving up zswap_entry_cache_alloc()? It can save compression processing time if zswap_entry_cache_alloc() is failed. > + > + /* populate entry */ > + entry->type = type; > + entry->offset = offset; > + entry->handle = handle; > + entry->length = dlen; > + > + /* map */ > + spin_lock(&tree->lock); > + do { > + ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry); > + if (ret == -EEXIST) { > + zswap_duplicate_entry++; > + > + /* remove from rbtree */ > + rb_erase(&dupentry->rbnode, &tree->rbroot); > + > + /* free */ > + zs_free(tree->pool, dupentry->handle); > + zswap_entry_cache_free(dupentry); > + atomic_dec(&zswap_stored_pages); > + } > + } while (ret == -EEXIST); > + spin_unlock(&tree->lock); > + > + /* update stats */ > + atomic_inc(&zswap_stored_pages); > + > + return 0; > + > +putcpu: > + put_cpu_var(zswap_dstmem); > +reject: > + return ret; > +} > + > +/* > + * returns 0 if the page was successfully decompressed > + * return -1 on entry not found or error > +*/ > +static int zswap_frontswap_load(unsigned type, pgoff_t offset, > + struct page *page) > +{ > + struct zswap_tree *tree = zswap_trees[type]; > + struct zswap_entry *entry; > + u8 *src, *dst; > + unsigned int dlen; > + > + /* find */ > + spin_lock(&tree->lock); > + entry = zswap_rb_search(&tree->rbroot, offset); > + spin_unlock(&tree->lock); > + > + /* decompress */ > + dlen = PAGE_SIZE; > + src = zs_map_object(tree->pool, entry->handle, ZS_MM_RO); > + dst = kmap_atomic(page); > + zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length, > + dst, &dlen); > + kunmap_atomic(dst); > + zs_unmap_object(tree->pool, entry->handle); > + > + return 0; > +} > + > +/* invalidates a single page */ > +static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset) > +{ > + struct zswap_tree *tree = zswap_trees[type]; > + struct zswap_entry *entry; > + > + /* find */ > + spin_lock(&tree->lock); > + entry = zswap_rb_search(&tree->rbroot, offset); > + > + /* remove from rbtree */ > + rb_erase(&entry->rbnode, &tree->rbroot); > + spin_unlock(&tree->lock); > + > + /* free */ > + zs_free(tree->pool, entry->handle); > + zswap_entry_cache_free(entry); > + atomic_dec(&zswap_stored_pages); > +} > + > +/* invalidates all pages for the given swap type */ > +static void zswap_frontswap_invalidate_area(unsigned type) > +{ > + struct zswap_tree *tree = zswap_trees[type]; > + struct rb_node *node; > + struct zswap_entry *entry; > + > + if (!tree) > + return; > + > + /* walk the tree and free everything */ > + spin_lock(&tree->lock); > + /* > + * TODO: Even though this code should not be executed because > + * the try_to_unuse() in swapoff should have emptied the tree, > + * it is very wasteful to rebalance the tree after every > + * removal when we are freeing the whole tree. > + * > + * If post-order traversal code is ever added to the rbtree > + * implementation, it should be used here. > + */ > + while ((node = rb_first(&tree->rbroot))) { > + entry = rb_entry(node, struct zswap_entry, rbnode); > + rb_erase(&entry->rbnode, &tree->rbroot); > + zs_free(tree->pool, entry->handle); > + zswap_entry_cache_free(entry); > + } You should decrease zswap_stored_pages in while loop. > + tree->rbroot = RB_ROOT; > + spin_unlock(&tree->lock); > +} > + > +/* NOTE: this is called in atomic context from swapon and must not sleep */ > +static void zswap_frontswap_init(unsigned type) > +{ > + struct zswap_tree *tree; > + > + tree = kzalloc(sizeof(struct zswap_tree), GFP_NOWAIT); > + if (!tree) > + goto err; > + tree->pool = zs_create_pool(GFP_NOWAIT, &zswap_zs_ops); > + if (!tree->pool) > + goto freetree; > + tree->rbroot = RB_ROOT; > + spin_lock_init(&tree->lock); > + zswap_trees[type] = tree; > + return; > + > +freetree: > + kfree(tree); > +err: > + pr_err("alloc failed, zswap disabled for swap type %d\n", type); > +} > + > +static struct frontswap_ops zswap_frontswap_ops = { > + .store = zswap_frontswap_store, > + .load = zswap_frontswap_load, > + .invalidate_page = zswap_frontswap_invalidate_page, > + .invalidate_area = zswap_frontswap_invalidate_area, > + .init = zswap_frontswap_init > +}; > + > +/********************************* > +* debugfs functions > +**********************************/ > +#ifdef CONFIG_DEBUG_FS > +#include <linux/debugfs.h> > + > +static struct dentry *zswap_debugfs_root; > + > +static int __init zswap_debugfs_init(void) > +{ > + if (!debugfs_initialized()) > + return -ENODEV; > + > + zswap_debugfs_root = debugfs_create_dir("zswap", NULL); > + if (!zswap_debugfs_root) > + return -ENOMEM; > + > + debugfs_create_u64("pool_limit_hit", S_IRUGO, > + zswap_debugfs_root, &zswap_pool_limit_hit); > + debugfs_create_u64("reject_zsmalloc_fail", S_IRUGO, > + zswap_debugfs_root, &zswap_reject_zsmalloc_fail); > + debugfs_create_u64("reject_kmemcache_fail", S_IRUGO, > + zswap_debugfs_root, &zswap_reject_kmemcache_fail); > + debugfs_create_u64("reject_compress_poor", S_IRUGO, > + zswap_debugfs_root, &zswap_reject_compress_poor); > + debugfs_create_u64("duplicate_entry", S_IRUGO, > + zswap_debugfs_root, &zswap_duplicate_entry); > + debugfs_create_atomic_t("pool_pages", S_IRUGO, > + zswap_debugfs_root, &zswap_pool_pages); > + debugfs_create_atomic_t("stored_pages", S_IRUGO, > + zswap_debugfs_root, &zswap_stored_pages); > + > + return 0; > +} > + > +static void __exit zswap_debugfs_exit(void) > +{ > + debugfs_remove_recursive(zswap_debugfs_root); > +} > +#else > +static inline int __init zswap_debugfs_init(void) > +{ > + return 0; > +} > + > +static inline void __exit zswap_debugfs_exit(void) { } > +#endif > + > +/********************************* > +* module init and exit > +**********************************/ > +static int __init init_zswap(void) > +{ > + if (!zswap_enabled) > + return 0; > + > + pr_info("loading zswap\n"); > + if (zswap_entry_cache_create()) { > + pr_err("entry cache creation failed\n"); > + goto error; > + } > + if (zswap_page_pool_create()) { > + pr_err("page pool initialization failed\n"); > + goto pagepoolfail; > + } > + if (zswap_comp_init()) { > + pr_err("compressor initialization failed\n"); > + goto compfail; > + } > + if (zswap_cpu_init()) { > + pr_err("per-cpu initialization failed\n"); > + goto pcpufail; > + } > + frontswap_register_ops(&zswap_frontswap_ops); > + if (zswap_debugfs_init()) > + pr_warn("debugfs initialization failed\n"); > + return 0; > +pcpufail: > + zswap_comp_exit(); > +compfail: > + zswap_page_pool_destroy(); > +pagepoolfail: > + zswap_entry_cache_destory(); > +error: > + return -ENOMEM; > +} > +/* must be late so crypto has time to come up */ > +late_initcall(init_zswap); > + > +MODULE_LICENSE("GPL"); > +MODULE_AUTHOR("Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>"); > +MODULE_DESCRIPTION("Compressed cache for swap pages"); > -- > 1.8.1.1 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>