lkml.org 
[lkml]   [2007]   [Aug]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[2.6.20.17 review 31/58] 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>
---
mm/readahead.c | 12 ++++++++++--
1 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/mm/readahead.c b/mm/readahead.c
index 0f539e8..f26cdea 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)
--
1.5.2.5
--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-08-22 11:15    [from the cache]
©2003-2011 Jasper Spaans