Re: [PATCH 3/4] cleanup ahead window calculation

[Steven Pratt]

Not sure how much better this is, but it doesn't hurt anything.

Steve

Oleg Nesterov wrote:

This patch moves some code into the get_next_ra_size()
and renames it into 'set_next_ahead_window'.

Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]>

--- 2.6.11-rc2/mm/readahead.c~  2005-01-25 15:17:13.000000000 +0300
+++ 2.6.11-rc2/mm/readahead.c   2005-01-25 16:51:50.000000000 +0300
@@ -85,20 +85,23 @@ static unsigned long get_init_ra_size(un
 * not for each call to readahead.  If a cache miss occured, reduce next I/O
 * size, else increase depending on how close to max we are.
 */
-static unsigned long get_next_ra_size(unsigned long cur, unsigned long max,
-                               unsigned long min, unsigned long * flags)
+static void set_next_ahead_window(struct file_ra_state *ra,
+                               unsigned long max, unsigned long min)
{
        unsigned long newsize;
+       unsigned long cur = ra->size;

-       if (*flags & RA_FLAG_MISS) {
+       ra->ahead_start = ra->start + cur;
+
+       if (ra->flags & RA_FLAG_MISS) {
+               ra->flags &= ~RA_FLAG_MISS;
                newsize = max((cur - 2), min);
-               *flags &= ~RA_FLAG_MISS;
-       } else if (cur < max / 16) {
+       } else if (cur < max / 16)
                newsize = 4 * cur;
-       } else {
+       else
                newsize = 2 * cur;
-       }
-       return min(newsize, max);
+
+       ra->ahead_size = min(newsize, max);
}

#define list_to_page(head) (list_entry((head)->prev, struct page, lru))
@@ -457,9 +460,7 @@ page_cache_readahead(struct address_spac
                 * immediately.
                 */
                if (req_size >= max) {
-                       ra->ahead_size = get_next_ra_size(ra->size, max, min,
-                                                         &ra->flags);
-                       ra->ahead_start = ra->start + ra->size;
+                       set_next_ahead_window(ra, max, min);
                        blockable_page_cache_readahead(mapping, filp,
                                 ra->ahead_start, ra->ahead_size, ra, 1);
                }
@@ -497,9 +498,7 @@ page_cache_readahead(struct address_spac
                        ra->size = ra->ahead_size;
                }

-               ra->ahead_size = get_next_ra_size(ra->size, max, min,
-                                                       &ra->flags);
-               ra->ahead_start = ra->start + ra->size;
+               set_next_ahead_window(ra, max, min);

block = ((offset + newsize - 1) >= ra->ahead_start);
if (!blockable_page_cache_readahead(mapping, filp,

-
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