diff options
| -rw-r--r-- | include/linux/fs.h | 64 | ||||
| -rw-r--r-- | mm/readahead.c | 19 |
2 files changed, 83 insertions, 0 deletions
diff --git a/include/linux/fs.h b/include/linux/fs.h index 75dd16efc9b6..9a5f562abc77 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 diff --git a/mm/readahead.c b/mm/readahead.c index 7f9bf588c936..072ce8f8357d 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -592,3 +592,22 @@ unsigned long max_sane_readahead(unsigned long nr) return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE) + node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2); } + +/* + * Submit IO for the read-ahead request in file_ra_state. + */ +unsigned long ra_submit(struct file_ra_state *ra, + struct address_space *mapping, struct file *filp) +{ + unsigned long ra_size; + unsigned long la_size; + int actual; + + ra_size = ra_readahead_size(ra); + la_size = ra_lookahead_size(ra); + actual = __do_page_cache_readahead(mapping, filp, + ra->ra_index, ra_size, la_size); + + return actual; +} +EXPORT_SYMBOL_GPL(ra_submit); |