From: Dan Magenheimer Subject: [PATCH V5 3/8] Cleancache: core ops functions and configuration Date: Fri, 3 Sep 2010 13:02:43 -0700 Message-ID: <20100903200243.GA4597__17226.54247792$1283544408$gmane$org@ca-server1.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: chris.mason@oracle.com, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, adilger@sun.com, tytso@mit.edu, mfasheh@suse.com, joel.becker@oracle.com, matthew@wil.cx, linux-btrfs@vger. Return-path: Received: from rcsinet10.oracle.com ([148.87.113.121]:53008 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756833Ab0ICUFJ (ORCPT ); Fri, 3 Sep 2010 16:05:09 -0400 Content-Disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: [PATCH V5 3/8] Cleancache: core ops functions and configuration Cleancache core ops functions and configuration Credits: Cleancache_ops design derived from Jeremy Fitzhardinge design for tmem; sysfs code modelled after mm/ksm.c Note that CONFIG_CLEANCACHE defaults to on; all hooks devolve to a compare-function-pointer-to-NULL so performance impact should be negligible, but can be reduced to zero impact if config'ed off. Signed-off-by: Dan Magenheimer Diffstat: include/linux/cleancache.h | 118 +++++++++ mm/Kconfig | 22 + mm/Makefile | 1 mm/cleancache.c | 258 +++++++++++++++++++++ 4 files changed, 399 insertions(+) --- linux-2.6.36-rc3/include/linux/cleancache.h 1969-12-31 17:00:00.000000000 -0700 +++ linux-2.6.36-rc3-cleancache/include/linux/cleancache.h 2010-09-02 14:44:59.000000000 -0600 @@ -0,0 +1,118 @@ +#ifndef _LINUX_CLEANCACHE_H +#define _LINUX_CLEANCACHE_H + +#include +#include +#include + +#define CLEANCACHE_KEY_MAX 6 + +/* + * cleancache requires every file with a page in cleancache to have a + * unique key unless/until the file is removed/truncated. For some + * filesystems, the inode number is unique, but for "modern" filesystems + * an exportable filehandle is required (see exportfs.h) + */ +struct cleancache_filekey { + union { + ino_t ino; + __u32 fh[CLEANCACHE_KEY_MAX]; + u32 key[CLEANCACHE_KEY_MAX]; + } u; +}; + +struct cleancache_ops { + int (*init_fs)(size_t); + int (*init_shared_fs)(char *uuid, size_t); + int (*get_page)(int, struct cleancache_filekey, + pgoff_t, struct page *); + void (*put_page)(int, struct cleancache_filekey, + pgoff_t, struct page *); + void (*flush_page)(int, struct cleancache_filekey, pgoff_t); + void (*flush_inode)(int, struct cleancache_filekey); + void (*flush_fs)(int); +}; + +extern struct cleancache_ops + cleancache_register_ops(struct cleancache_ops *ops); +extern void __cleancache_init_fs(struct super_block *); +extern void __cleancache_init_shared_fs(char *, struct super_block *); +extern int __cleancache_get_page(struct page *); +extern void __cleancache_put_page(struct page *); +extern void __cleancache_flush_page(struct address_space *, struct page *); +extern void __cleancache_flush_inode(struct address_space *); +extern void __cleancache_flush_fs(struct super_block *); +extern int cleancache_enabled; + +#ifdef CONFIG_CLEANCACHE +#define cleancache_fs_enabled(_page) \ + (_page->mapping->host->i_sb->cleancache_poolid >= 0) +#define cleancache_fs_enabled_mapping(_mapping) \ + (mapping->host->i_sb->cleancache_poolid >= 0) +#else +#define cleancache_enabled (0) +#define cleancache_fs_enabled(_page) (0) +#define cleancache_fs_enabled_mapping(_page) (0) +#endif + +/* + * The shim layer provided by these inline functions allows the compiler + * to reduce all cleancache hooks to nothingness if CONFIG_CLEANCACHE + * is disabled, to a single global variable check if CONFIG_CLEANCACHE + * is enabled but no cleancache "backend" has dynamically enabled it, + * and, for the most frequent cleancache ops, to a single global variable + * check plus a superblock element comparison if CONFIG_CLEANCACHE is enabled + * and a cleancache backend has dynamically enabled cleancache, but the + * filesystem referenced by that cleancache op has not enabled cleancache. + * As a result, CONFIG_CLEANCACHE can be enabled by default with essentially + * no measurable performance impact. + */ + +static inline void cleancache_init_fs(struct super_block *sb) +{ + if (cleancache_enabled) + __cleancache_init_fs(sb); +} + +static inline void cleancache_init_shared_fs(char *uuid, struct super_block *sb) +{ + if (cleancache_enabled) + __cleancache_init_shared_fs(uuid, sb); +} + +static inline int cleancache_get_page(struct page *page) +{ + int ret = -1; + + if (cleancache_enabled && cleancache_fs_enabled(page)) + ret = __cleancache_get_page(page); + return ret; +} + +static inline void cleancache_put_page(struct page *page) +{ + if (cleancache_enabled && cleancache_fs_enabled(page)) + __cleancache_put_page(page); +} + +static inline void cleancache_flush_page(struct address_space *mapping, + struct page *page) +{ + /* careful... page->mapping is NULL sometimes when this is called */ + if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping)) + __cleancache_flush_page(mapping, page); +} + +static inline void cleancache_flush_inode(struct address_space *mapping) +{ + if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping)) + __cleancache_flush_inode(mapping); +} + +static inline void cleancache_flush_fs(struct super_block *sb) +{ + if (cleancache_enabled) + __cleancache_flush_fs(sb); +} + +#endif /* _LINUX_CLEANCACHE_H */ --- linux-2.6.36-rc3/mm/cleancache.c 1969-12-31 17:00:00.000000000 -0700 +++ linux-2.6.36-rc3-cleancache/mm/cleancache.c 2010-09-02 14:46:50.000000000 -0600 @@ -0,0 +1,258 @@ +/* + * Cleancache frontend + * + * This code provides the generic "frontend" layer to call a matching + * "backend" driver implementation of cleancache. See + * Documentation/vm/cleancache.txt for more information. + * + * Copyright (C) 2009-2010 Oracle Corp. All rights reserved. + * Author: Dan Magenheimer + * + * This work is licensed under the terms of the GNU GPL, version 2. + */ + +#include +#include +#include +#include +#include + +/* + * This global enablement flag may be read thousands of times per second + * by cleancache_get/put/flush even on systems where cleancache_ops + * is not claimed (e.g. cleancache is config'ed on but remains + * disabled), so is preferred to the slower alternative: a function + * call that checks a non-global. + */ +int cleancache_enabled; +EXPORT_SYMBOL(cleancache_enabled); + +/* + * cleancache_ops is set by cleancache_ops_register to contain the pointers + * to the cleancache "backend" implementation functions. + */ +static struct cleancache_ops cleancache_ops; + +/* useful stats available in /sys/kernel/mm/cleancache */ +static unsigned long cleancache_succ_gets; +static unsigned long cleancache_failed_gets; +static unsigned long cleancache_puts; +static unsigned long cleancache_flushes; + +/* + * register operations for cleancache, returning previous thus allowing + * detection of multiple backends and possible nesting + */ +struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops) +{ + struct cleancache_ops old = cleancache_ops; + + cleancache_ops = *ops; + cleancache_enabled = 1; + return old; +} +EXPORT_SYMBOL(cleancache_register_ops); + +/* Called by a cleancache-enabled filesystem at time of mount */ +void __cleancache_init_fs(struct super_block *sb) +{ + sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE); +} +EXPORT_SYMBOL(__cleancache_init_fs); + +/* Called by a cleancache-enabled clustered filesystem at time of mount */ +void __cleancache_init_shared_fs(char *uuid, struct super_block *sb) +{ + sb->cleancache_poolid = + (*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE); +} +EXPORT_SYMBOL(__cleancache_init_shared_fs); + +/* + * If the filesystem uses exportable filehandles, use the filehandle as + * the key, else use the inode number. + */ +static int cleancache_get_key(struct inode *inode, + struct cleancache_filekey *key) +{ + int (*fhfn)(struct dentry *, __u32 *fh, int *, int); + int maxlen = CLEANCACHE_KEY_MAX; + struct super_block *sb = inode->i_sb; + struct dentry *d; + + key->u.ino = inode->i_ino; + if (sb->s_export_op != NULL) { + fhfn = sb->s_export_op->encode_fh; + if (fhfn) { + d = list_first_entry(&inode->i_dentry, + struct dentry, d_alias); + (void)(*fhfn)(d, &key->u.fh[0], &maxlen, 0); + if (maxlen > CLEANCACHE_KEY_MAX) + return -1; + } + } + return 0; +} + +/* + * "Get" data from cleancache associated with the poolid/inode/index + * that were specified when the data was put to cleanache and, if + * successful, use it to fill the specified page with data and return 0. + * The pageframe is unchanged and returns -1 if the get fails. + * Page must be locked by caller. + */ +int __cleancache_get_page(struct page *page) +{ + int ret = -1; + int pool_id; + struct cleancache_filekey key = { .u.key = { 0 } }; + + VM_BUG_ON(!PageLocked(page)); + pool_id = page->mapping->host->i_sb->cleancache_poolid; + if (pool_id < 0) + goto out; + + if (cleancache_get_key(page->mapping->host, &key) < 0) + goto out; + + ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page); + if (ret == 0) + cleancache_succ_gets++; + else + cleancache_failed_gets++; +out: + return ret; +} +EXPORT_SYMBOL(__cleancache_get_page); + +/* + * "Put" data from a page to cleancache and associate it with the + * (previously-obtained per-filesystem) poolid and the page's, + * inode and page index. Page must be locked. Note that a put_page + * always "succeeds", though a subsequent get_page may succeed or fail. + */ +void __cleancache_put_page(struct page *page) +{ + int pool_id; + struct cleancache_filekey key = { .u.key = { 0 } }; + + VM_BUG_ON(!PageLocked(page)); + pool_id = page->mapping->host->i_sb->cleancache_poolid; + if (pool_id >= 0 && + cleancache_get_key(page->mapping->host, &key) >= 0) { + (*cleancache_ops.put_page)(pool_id, key, page->index, page); + cleancache_puts++; + } +} +EXPORT_SYMBOL(__cleancache_put_page); + +/* + * Flush any data from cleancache associated with the poolid and the + * page's inode and page index so that a subsequent "get" will fail. + */ +void __cleancache_flush_page(struct address_space *mapping, struct page *page) +{ + /* careful... page->mapping is NULL sometimes when this is called */ + int pool_id = mapping->host->i_sb->cleancache_poolid; + struct cleancache_filekey key = { .u.key = { 0 } }; + + if (pool_id >= 0) { + VM_BUG_ON(!PageLocked(page)); + if (cleancache_get_key(mapping->host, &key) >= 0) { + (*cleancache_ops.flush_page)(pool_id, key, page->index); + cleancache_flushes++; + } + } +} +EXPORT_SYMBOL(__cleancache_flush_page); + +/* + * Flush all data from cleancache associated with the poolid and the + * mappings's inode so that all subsequent gets to this poolid/inode + * will fail. + */ +void __cleancache_flush_inode(struct address_space *mapping) +{ + int pool_id = mapping->host->i_sb->cleancache_poolid; + struct cleancache_filekey key = { .u.key = { 0 } }; + + if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0) + (*cleancache_ops.flush_inode)(pool_id, key); +} +EXPORT_SYMBOL(__cleancache_flush_inode); + +/* + * Called by any cleancache-enabled filesystem at time of unmount; + * note that pool_id is surrendered and may be reutrned by a subsequent + * cleancache_init_fs or cleancache_init_shared_fs + */ +void __cleancache_flush_fs(struct super_block *sb) +{ + if (sb->cleancache_poolid >= 0) { + int old_poolid = sb->cleancache_poolid; + sb->cleancache_poolid = -1; + (*cleancache_ops.flush_fs)(old_poolid); + } +} +EXPORT_SYMBOL(__cleancache_flush_fs); + +#ifdef CONFIG_SYSFS + +/* see Documentation/ABI/xxx/sysfs-kernel-mm-cleancache */ + +#define CLEANCACHE_ATTR_RO(_name) \ + static struct kobj_attribute _name##_attr = __ATTR_RO(_name) + +static ssize_t cleancache_succ_gets_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", cleancache_succ_gets); +} +CLEANCACHE_ATTR_RO(cleancache_succ_gets); + +static ssize_t cleancache_failed_gets_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", cleancache_failed_gets); +} +CLEANCACHE_ATTR_RO(cleancache_failed_gets); + +static ssize_t cleancache_puts_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", cleancache_puts); +} +CLEANCACHE_ATTR_RO(cleancache_puts); + +static ssize_t cleancache_flushes_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", cleancache_flushes); +} +CLEANCACHE_ATTR_RO(cleancache_flushes); + +static struct attribute *cleancache_attrs[] = { + &cleancache_succ_gets_attr.attr, + &cleancache_failed_gets_attr.attr, + &cleancache_puts_attr.attr, + &cleancache_flushes_attr.attr, + NULL, +}; + +static struct attribute_group cleancache_attr_group = { + .attrs = cleancache_attrs, + .name = "cleancache", +}; + +#endif /* CONFIG_SYSFS */ + +static int __init init_cleancache(void) +{ +#ifdef CONFIG_SYSFS + int err; + + err = sysfs_create_group(mm_kobj, &cleancache_attr_group); +#endif /* CONFIG_SYSFS */ + return 0; +} +module_init(init_cleancache) --- linux-2.6.36-rc3/mm/Kconfig 2010-08-29 09:36:04.000000000 -0600 +++ linux-2.6.36-rc3-cleancache/mm/Kconfig 2010-08-30 09:20:43.000000000 -0600 @@ -301,3 +301,25 @@ config NOMMU_INITIAL_TRIM_EXCESS of 1 says that all excess pages should be trimmed. See Documentation/nommu-mmap.txt for more information. + +config CLEANCACHE + bool "Enable cleancache pseudo-RAM driver to cache clean pages" + default y + help + Cleancache can be thought of as a page-granularity victim cache + for clean pages that the kernel's pageframe replacement algorithm + (PFRA) would like to keep around, but can't since there isn't enough + memory. So when the PFRA "evicts" a page, it first attempts to put + it into a synchronous concurrency-safe page-oriented pseudo-RAM + device (such as Xen's Transcendent Memory, aka "tmem") which is not + directly accessible or addressable by the kernel and is of unknown + (and possibly time-varying) size. And when a cleancache-enabled + filesystem wishes to access a page in a file on disk, it first + checks cleancache to see if it already contains it; if it does, + the page is copied into the kernel and a disk access is avoided. + When a pseudo-RAM device is available, a significant I/O reduction + may be achieved. When none is available, all cleancache calls + are reduced to a single pointer-compare-against-NULL resulting + in a negligible performance hit. + + If unsure, say Y to enable cleancache --- linux-2.6.36-rc3/mm/Makefile 2010-08-29 09:36:04.000000000 -0600 +++ linux-2.6.36-rc3-cleancache/mm/Makefile 2010-08-30 09:20:43.000000000 -0600 @@ -47,3 +47,4 @@ obj-$(CONFIG_MEMORY_FAILURE) += memory-f obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o +obj-$(CONFIG_CLEANCACHE) += cleancache.o