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authorFengguang Wu <wfg@mail.ustc.edu.cn>2007-07-19 01:47:58 -0700
committerWilly Tarreau <w@1wt.eu>2007-08-25 17:24:10 +0200
commitfaae60c8fef63043850b17b105f42c075d4d74f9 (patch)
tree818bc6c81b46d1e772072601a413c90c8eb32d37
parent25d919bd316afa283e1d758967923fddcff83fd8 (diff)
[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.c12
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)