From: Jeremy Fitzhardinge Subject: Re: [PATCH V4 3/8] Cleancache: core ops functions and configuration Date: Mon, 30 Aug 2010 15:48:01 -0700 Message-ID: <4C7C3521.7090403@goop.org> References: <20100830223133.GA1272@ca-server1.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: 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.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, ocfs2-devel@oss.oracle.com, linux-mm@kvack.org, ngupta@vflare.org, JBeulich@novell.com, kurt.hackel@oracle.com, npiggin@kernel.dk, dave.mccracken@oracle.com, riel@redhat.com, avi@redhat.com, konrad.wilk@oracle.com, mel@csn.ul.ie, yinghan@google.com, gthelen@google.com To: Dan Magenheimer Return-path: In-Reply-To: <20100830223133.GA1272@ca-server1.us.oracle.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 08/30/2010 03:31 PM, Dan Magenheimer wrote: > [PATCH V4 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 | 101 ++++++++++ > mm/Kconfig | 22 ++ > mm/Makefile | 1 > mm/cleancache.c | 201 +++++++++++++++++++++ > 4 files changed, 325 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 2010-08-30 14:54:31.000000000 -0600 > @@ -0,0 +1,101 @@ > +#ifndef _LINUX_CLEANCACHE_H > +#define _LINUX_CLEANCACHE_H > + > +#include > +#include > +#include > + > +#define CLEANCACHE_KEY_MAX 6 > + > +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_ops; > +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 *); > + > +#ifdef CONFIG_CLEANCACHE > +#define cleancache_enabled (cleancache_ops.init_fs) Pointers can be used in a boolean context, but it would probably be cleaner to have this evaluate to a proper boolean type. Also I'd probably go with an all-caps macro name rather than making it look like a variable. > +#else > +#define cleancache_enabled (0) > +#endif > + > +/* called by a cleancache-enabled filesystem at time of mount */ > +static inline int cleancache_init_fs(size_t pagesize) > +{ > + int ret = -1; > + > + if (cleancache_enabled) > + ret = (*cleancache_ops.init_fs)(pagesize); > + return ret; > +} > + > +/* called by a cleancache-enabled clustered filesystem at time of mount */ > +static inline int cleancache_init_shared_fs(char *uuid, size_t pagesize) > +{ > + int ret = -1; > + > + if (cleancache_enabled) > + ret = (*cleancache_ops.init_shared_fs)(uuid, pagesize); > + return ret; > +} > + > +static inline int cleancache_get_page(struct page *page) > +{ > + int ret = -1; > + > + if (cleancache_enabled) > + ret = __cleancache_get_page(page); > + return ret; > +} > + > +static inline void cleancache_put_page(struct page *page) > +{ > + if (cleancache_enabled) > + __cleancache_put_page(page); > +} > + > +static inline void cleancache_flush_page(struct address_space *mapping, > + struct page *page) > +{ > + if (cleancache_enabled) > + __cleancache_flush_page(mapping, page); > +} > + > +static inline void cleancache_flush_inode(struct address_space *mapping) > +{ > + if (cleancache_enabled) > + __cleancache_flush_inode(mapping); > +} > + > +/* > + * called by any cleancache-enabled filesystem at time of unmount; > + * note that pool_id is surrendered and may be returned by a subsequent > + * cleancache_init_fs or cleancache_init_shared_fs > + */ > +static inline void cleancache_flush_fs(int pool_id) > +{ > + if (cleancache_enabled && pool_id >= 0) > + (*cleancache_ops.flush_fs)(pool_id); > +} > + > +#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 2010-08-30 14:58:40.000000000 -0600 > @@ -0,0 +1,201 @@ > +/* > + * 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 > + > +/* > + * cleancache_ops contains the pointers to the cleancache "backend" > + * implementation functions. This global variable may be checked thousands > + * of times per second by cleancache_get/put/flush_page even on systems > + * where cleancache_ops is not claimed (e.g. cleancache stays disabled), > + * so is preferred to the slower alternative: a function call that > + * checks a non-global. > + */ > +struct cleancache_ops cleancache_ops; > + > +/* useful stats available in /sys/kernel/mm/cleancache */ > +static unsigned long succ_gets; > +static unsigned long failed_gets; > +static unsigned long puts; > +static unsigned long flushes; I'd probably give these very generic-sounding names some slightly unique prefix just to help out people looking at "nm" output or using ctags. > + > +/* > + * If the filesystem uses exportable filehandles, use the filehandle as > + * the key, else use the inode number. > + */ > +static int get_key(struct inode *inode, struct cleancache_filekey *key) Ditto. > +{ > + int (*fhfn)(struct dentry *, __u32 *fh, int *, int); > + int maxlen = CLEANCACHE_KEY_MAX; > + struct super_block *sb = inode->i_sb; > + struct dentry *d; > + > + if (sb->s_export_op && (fhfn = sb->s_export_op->encode_fh)) { > + 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; > + } > + else > + key->u.ino = inode->i_ino; > + 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 (get_key(page->mapping->host,&key) < 0) > + goto out; > + > + ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page); > + if (ret == 0) > + succ_gets++; > + else > + 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 && get_key(page->mapping->host,&key) >= 0) { > + (*cleancache_ops.put_page)(pool_id, key, page->index, page); > + puts++; > + } > +} > + > +/* > + * 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) > +{ > + 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 (get_key(page->mapping->host,&key) >= 0) { > + (*cleancache_ops.flush_page)(pool_id, key, page->index); > + 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 && get_key(mapping->host,&key) >= 0) > + (*cleancache_ops.flush_inode)(pool_id, key); > +} > +EXPORT_SYMBOL(__cleancache_flush_inode); > + > +#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 succ_gets_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%lu\n", succ_gets); > +} > +CLEANCACHE_ATTR_RO(succ_gets); > + > +static ssize_t failed_gets_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%lu\n", failed_gets); > +} > +CLEANCACHE_ATTR_RO(failed_gets); > + > +static ssize_t puts_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%lu\n", puts); > +} > +CLEANCACHE_ATTR_RO(puts); > + > +static ssize_t flushes_show(struct kobject *kobj, > + struct kobj_attribute *attr, char *buf) > +{ > + return sprintf(buf, "%lu\n", flushes); > +} > +CLEANCACHE_ATTR_RO(flushes); > + > +static struct attribute *cleancache_attrs[] = { > + &succ_gets_attr.attr, > + &failed_gets_attr.attr, > + &puts_attr.attr, > + &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 >