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author | Fengguang Wu <wfg@mail.ustc.edu.cn> | 2007-07-19 01:47:59 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-19 10:04:44 -0700 |
commit | 5ce1110b92b31d079aa443e967f43a2294e01194 (patch) | |
tree | eff95b4c8ede07d0777ca68a30d686d1acbb5c73 /include/linux/fs.h | |
parent | f615bfca468c9b80ed2d09be5fdbaf470a32c045 (diff) | |
download | op-kernel-dev-5ce1110b92b31d079aa443e967f43a2294e01194.zip op-kernel-dev-5ce1110b92b31d079aa443e967f43a2294e01194.tar.gz |
readahead: data structure and routines
Extend struct file_ra_state to support the on-demand readahead logic. Also
define some helpers for it.
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Steven Pratt <slpratt@austin.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/fs.h')
-rw-r--r-- | include/linux/fs.h | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 75dd16e..9a5f562 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -695,6 +695,10 @@ struct fown_struct { /* * Track a single file's readahead state + * + * ================#============|==================#==================| + * ^ ^ ^ ^ + * file_ra_state.la_index .ra_index .lookahead_index .readahead_index */ struct file_ra_state { unsigned long start; /* Current window */ @@ -704,6 +708,12 @@ struct file_ra_state { unsigned long prev_index; /* Cache last read() position */ unsigned long ahead_start; /* Ahead window */ unsigned long ahead_size; + + pgoff_t la_index; /* enqueue time */ + pgoff_t ra_index; /* begin offset */ + pgoff_t lookahead_index; /* time to do next readahead */ + pgoff_t readahead_index; /* end offset */ + unsigned long ra_pages; /* Maximum readahead window */ unsigned long mmap_hit; /* Cache hit stat for mmap accesses */ unsigned long mmap_miss; /* Cache miss stat for mmap accesses */ @@ -712,6 +722,60 @@ struct file_ra_state { #define RA_FLAG_MISS 0x01 /* a cache miss occured against this file */ #define RA_FLAG_INCACHE 0x02 /* file is already in cache */ +/* + * Measuring read-ahead sizes. + * + * |----------- readahead size ------------>| + * ===#============|==================#=====================| + * |------- invoke interval ------>|-- lookahead size -->| + */ +static inline unsigned long ra_readahead_size(struct file_ra_state *ra) +{ + return ra->readahead_index - ra->ra_index; +} + +static inline unsigned long ra_lookahead_size(struct file_ra_state *ra) +{ + return ra->readahead_index - ra->lookahead_index; +} + +static inline unsigned long ra_invoke_interval(struct file_ra_state *ra) +{ + return ra->lookahead_index - ra->la_index; +} + +/* + * Check if @index falls in the readahead windows. + */ +static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index) +{ + return (index >= ra->la_index && + index < ra->readahead_index); +} + +/* + * Where is the old read-ahead and look-ahead? + */ +static inline void ra_set_index(struct file_ra_state *ra, + pgoff_t la_index, pgoff_t ra_index) +{ + ra->la_index = la_index; + ra->ra_index = ra_index; +} + +/* + * Where is the new read-ahead and look-ahead? + */ +static inline void ra_set_size(struct file_ra_state *ra, + unsigned long ra_size, unsigned long la_size) +{ + ra->readahead_index = ra->ra_index + ra_size; + ra->lookahead_index = ra->ra_index + ra_size - la_size; +} + +unsigned long ra_submit(struct file_ra_state *ra, + struct address_space *mapping, struct file *filp); + struct file { /* * fu_list becomes invalid after file_free is called and queued via |