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| author | Theodore Ts'o <tytso@mit.edu> | 2015-02-02 00:37:00 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2015-02-05 02:45:00 -0500 |
| commit | 0ae45f63d4ef8d8eeec49c7d8b44a1775fff13e8 (patch) | |
| tree | 660dbb014482092361eab263847fb906b5a9ec22 /include/linux | |
| parent | e36f014edff70fc02b3d3d79cead1d58f289332e (diff) | |
| download | lwn-0ae45f63d4ef8d8eeec49c7d8b44a1775fff13e8.tar.gz lwn-0ae45f63d4ef8d8eeec49c7d8b44a1775fff13e8.zip | |
vfs: add support for a lazytime mount option
Add a new mount option which enables a new "lazytime" mode. This mode
causes atime, mtime, and ctime updates to only be made to the
in-memory version of the inode. The on-disk times will only get
updated when (a) if the inode needs to be updated for some non-time
related change, (b) if userspace calls fsync(), syncfs() or sync(), or
(c) just before an undeleted inode is evicted from memory.
This is OK according to POSIX because there are no guarantees after a
crash unless userspace explicitly requests via a fsync(2) call.
For workloads which feature a large number of random write to a
preallocated file, the lazytime mount option significantly reduces
writes to the inode table. The repeated 4k writes to a single block
will result in undesirable stress on flash devices and SMR disk
drives. Even on conventional HDD's, the repeated writes to the inode
table block will trigger Adjacent Track Interference (ATI) remediation
latencies, which very negatively impact long tail latencies --- which
is a very big deal for web serving tiers (for example).
Google-Bug-Id: 18297052
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/backing-dev.h | 1 | ||||
| -rw-r--r-- | include/linux/fs.h | 5 |
2 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 5da6012b7a14..4cdf7336f64a 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -55,6 +55,7 @@ struct bdi_writeback { struct list_head b_dirty; /* dirty inodes */ struct list_head b_io; /* parked for writeback */ struct list_head b_more_io; /* parked for more writeback */ + struct list_head b_dirty_time; /* time stamps are dirty */ spinlock_t list_lock; /* protects the b_* lists */ }; diff --git a/include/linux/fs.h b/include/linux/fs.h index 42efe13077b6..cd027ce2c705 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1746,8 +1746,12 @@ struct super_operations { #define __I_DIO_WAKEUP 9 #define I_DIO_WAKEUP (1 << I_DIO_WAKEUP) #define I_LINKABLE (1 << 10) +#define I_DIRTY_TIME (1 << 11) +#define __I_DIRTY_TIME_EXPIRED 12 +#define I_DIRTY_TIME_EXPIRED (1 << __I_DIRTY_TIME_EXPIRED) #define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES) +#define I_DIRTY_ALL (I_DIRTY | I_DIRTY_TIME) extern void __mark_inode_dirty(struct inode *, int); static inline void mark_inode_dirty(struct inode *inode) @@ -1910,6 +1914,7 @@ extern int current_umask(void); extern void ihold(struct inode * inode); extern void iput(struct inode *); +extern int generic_update_time(struct inode *, struct timespec *, int); static inline struct inode *file_inode(const struct file *f) { |