Re: Readahead algorithm problems again...

[Oleg Nesterov]

Oleg Nesterov wrote:
> 
> What do you think about this patch?

Ohh... Sorry, I attached the wrong one.

--- 2.6.13-rc4/mm/readahead.c~	Thu Apr  7 12:59:41 2005
+++ 2.6.13-rc4/mm/readahead.c	Thu Aug  4 20:25:14 2005
@@ -57,8 +57,8 @@ static inline void ra_off(struct file_ra
 	ra->start = 0;
 	ra->flags = 0;
 	ra->size = 0;
+	ra->ahead_size += ra->ahead_start;
 	ra->ahead_start = 0;
-	ra->ahead_size = 0;
 	return;
 }
 
@@ -423,8 +423,8 @@ static int make_ahead_window(struct addr
 		 * congestion.  The ahead window will any way be closed
 		 * in case we failed due to excessive page cache hits.
 		 */
+		ra->ahead_size += ra->ahead_start;
 		ra->ahead_start = 0;
-		ra->ahead_size = 0;
 	}
 
 	return ret;
@@ -507,7 +507,7 @@ page_cache_readahead(struct address_spac
 
 	if (ra->ahead_start == 0) {	 /* no ahead window yet */
 		if (!make_ahead_window(mapping, filp, ra, 0))
-			goto out;
+			goto recheck;
 	}
 	/*
 	 * Already have an ahead window, check if we crossed into it.
@@ -520,6 +520,9 @@ page_cache_readahead(struct address_spac
 		ra->start = ra->ahead_start;
 		ra->size = ra->ahead_size;
 		make_ahead_window(mapping, filp, ra, 0);
+recheck:
+		ra->prev_page = min(ra->prev_page,
+			ra->ahead_start + ra->ahead_size - 1);
 	}
 
 out:

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There is another one, from Steven Pratt:

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