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| author | Fengguang Wu <wfg@mail.ustc.edu.cn> | 2007-07-19 01:47:58 -0700 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2007-08-25 17:24:10 +0200 |
| commit | faae60c8fef63043850b17b105f42c075d4d74f9 (patch) | |
| tree | 818bc6c81b46d1e772072601a413c90c8eb32d37 | |
| parent | 25d919bd316afa283e1d758967923fddcff83fd8 (diff) | |
| download | lwn-faae60c8fef63043850b17b105f42c075d4d74f9.tar.gz lwn-faae60c8fef63043850b17b105f42c075d4d74f9.zip | |
[PATCH] readahead: MIN_RA_PAGES/MAX_RA_PAGES macros
Define two convenient macros for read-ahead:
- MAX_RA_PAGES: rounded down counterpart of VM_MAX_READAHEAD
- MIN_RA_PAGES: rounded _up_ counterpart of VM_MIN_READAHEAD
Note that the rounded up MIN_RA_PAGES will work flawlessly with _large_
page sizes like 64k.
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: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>
| -rw-r--r-- | mm/readahead.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/mm/readahead.c b/mm/readahead.c index 0f539e8e827a..f26cdea826b3 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -21,8 +21,16 @@ void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page) } EXPORT_SYMBOL(default_unplug_io_fn); +/* + * Convienent macros for min/max read-ahead pages. + * Note that MAX_RA_PAGES is rounded down, while MIN_RA_PAGES is rounded up. + * The latter is necessary for systems with large page size(i.e. 64k). + */ +#define MAX_RA_PAGES (VM_MAX_READAHEAD*1024 / PAGE_CACHE_SIZE) +#define MIN_RA_PAGES DIV_ROUND_UP(VM_MIN_READAHEAD*1024, PAGE_CACHE_SIZE) + struct backing_dev_info default_backing_dev_info = { - .ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE, + .ra_pages = MAX_RA_PAGES, .state = 0, .capabilities = BDI_CAP_MAP_COPY, .unplug_io_fn = default_unplug_io_fn, @@ -51,7 +59,7 @@ static inline unsigned long get_max_readahead(struct file_ra_state *ra) static inline unsigned long get_min_readahead(struct file_ra_state *ra) { - return (VM_MIN_READAHEAD * 1024) / PAGE_CACHE_SIZE; + return MIN_RA_PAGES; } static inline void reset_ahead_window(struct file_ra_state *ra) |