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The Linux 3.1 kernel has introduced the concept of per-filesystem shrinkers which are directly assoicated with a super block. Prior to this change there was one shared global shrinker. The zfs code relied on being able to call the global shrinker when the arc_meta_limit was exceeded. This would cause the VFS to drop references on a fraction of the dentries in the dcache. The ARC could then safely reclaim the memory used by these entries and honor the arc_meta_limit. Unfortunately, when per-filesystem shrinkers were added the old interfaces were made unavailable. This change adds support to use the new per-filesystem shrinker interface so we can continue to honor the arc_meta_limit. The major benefit of the new interface is that we can now target only the zfs filesystem for dentry and inode pruning. Thus we can minimize any impact on the caching of other filesystems. In the context of making this change several other important issues related to managing the ARC were addressed, they include: * The dnlc_reduce_cache() function which was called by the ARC to drop dentries for the Posix layer was replaced with a generic zfs_prune_t callback. The ZPL layer now registers a callback to drop these dentries removing a layering violation which dates back to the Solaris code. This callback can also be used by other ARC consumers such as Lustre. arc_add_prune_callback() arc_remove_prune_callback() * The arc_reduce_dnlc_percent module option has been changed to arc_meta_prune for clarity. The dnlc functions are specific to Solaris's VFS and have already been largely eliminated already. The replacement tunable now represents the number of bytes the prune callback will request when invoked. * Less aggressively invoke the prune callback. We used to call this whenever we exceeded the arc_meta_limit however that's not strictly correct since it results in over zeleous reclaim of dentries and inodes. It is now only called once the arc_meta_limit is exceeded and every effort has been made to evict other data from the ARC cache. * More promptly manage exceeding the arc_meta_limit. When reading meta data in to the cache if a buffer was unable to be recycled notify the arc_reclaim thread to invoke the required prune. * Added arcstat_prune kstat which is incremented when the ARC is forced to request that a consumer prune its cache. Remember this will only occur when the ARC has no other choice. If it can evict buffers safely without invoking the prune callback it will. * This change is also expected to resolve the unexpect collapses of the ARC cache. This would occur because when exceeded just the arc_meta_limit reclaim presure would be excerted on the arc_c value via arc_shrink(). This effectively shrunk the entire cache when really we just needed to reclaim meta data. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #466 Closes #292
70 lines
2.4 KiB
C
70 lines
2.4 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright (c) 2011, Lawrence Livermore National Security, LLC.
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*/
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#ifndef _SYS_ZPL_H
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#define _SYS_ZPL_H
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#include <sys/vfs.h>
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#include <linux/vfs_compat.h>
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#include <linux/xattr_compat.h>
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#include <linux/exportfs.h>
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#include <linux/writeback.h>
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/* zpl_inode.c */
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extern const struct inode_operations zpl_inode_operations;
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extern const struct inode_operations zpl_dir_inode_operations;
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extern const struct inode_operations zpl_symlink_inode_operations;
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extern const struct inode_operations zpl_special_inode_operations;
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/* zpl_file.c */
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extern ssize_t zpl_read_common(struct inode *ip, const char *buf,
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size_t len, loff_t pos, uio_seg_t segment, int flags, cred_t *cr);
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extern ssize_t zpl_write_common(struct inode *ip, const char *buf,
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size_t len, loff_t pos, uio_seg_t segment, int flags, cred_t *cr);
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extern const struct address_space_operations zpl_address_space_operations;
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extern const struct file_operations zpl_file_operations;
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extern const struct file_operations zpl_dir_file_operations;
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/* zpl_super.c */
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extern void zpl_prune_sbs(int64_t bytes_to_scan, void *private);
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typedef struct zpl_mount_data {
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const char *z_osname; /* Dataset name */
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void *z_data; /* Mount options string */
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} zpl_mount_data_t;
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extern const struct super_operations zpl_super_operations;
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extern const struct export_operations zpl_export_operations;
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extern struct file_system_type zpl_fs_type;
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/* zpl_xattr.c */
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extern ssize_t zpl_xattr_list(struct dentry *dentry, char *buf, size_t size);
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extern int zpl_xattr_security_init(struct inode *ip, struct inode *dip,
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const struct qstr *qstr);
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extern xattr_handler_t *zpl_xattr_handlers[];
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#endif /* _SYS_ZPL_H */
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