X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=mm%2Freadahead.c;h=a5e6906a01e03073ff399da20f75821efb47e2dc;hb=c7b5ebbddf7bcd3651947760f423e3783bbe6573;hp=71bf2462d0972519afa6683cbcf850c2be274b66;hpb=5273a3df6485dc2ad6aa7ddd441b9a21970f003b;p=linux-2.6.git

diff --git a/mm/readahead.c b/mm/readahead.c
index 71bf2462d..a5e6906a0 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -15,7 +15,7 @@
 #include <linux/backing-dev.h>
 #include <linux/pagevec.h>
 
-void default_unplug_io_fn(struct backing_dev_info *bdi)
+void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
 {
 }
 EXPORT_SYMBOL(default_unplug_io_fn);
@@ -28,16 +28,15 @@ struct backing_dev_info default_backing_dev_info = {
 EXPORT_SYMBOL_GPL(default_backing_dev_info);
 
 /*
- * Initialise a struct file's readahead state
+ * Initialise a struct file's readahead state.  Assumes that the caller has
+ * memset *ra to zero.
  */
 void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
 {
-	memset(ra, 0, sizeof(*ra));
 	ra->ra_pages = mapping->backing_dev_info->ra_pages;
 	ra->average = ra->ra_pages / 2;
 }
-EXPORT_SYMBOL(file_ra_state_init);
 
 /*
  * Return max readahead size for this inode in number-of-pages.
@@ -349,11 +348,10 @@ page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,
 			struct file *filp, unsigned long offset)
 {
 	unsigned max;
-	unsigned min;
 	unsigned orig_next_size;
 	unsigned actual;
 	int first_access=0;
-	unsigned long preoffset=0;
+	unsigned long average;
 
 	/*
 	 * Here we detect the case where the application is performing
@@ -374,7 +372,6 @@ page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,
 	if (max == 0)
 		goto out;	/* No readahead */
 
-	min = get_min_readahead(ra);
 	orig_next_size = ra->next_size;
 
 	if (ra->next_size == 0) {
@@ -386,18 +383,10 @@ page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,
 		first_access=1;
 		ra->next_size = max / 2;
 		ra->prev_page = offset;
-		ra->serial_cnt++;
+		ra->currnt_wnd_hit++;
 		goto do_io;
 	}
 
-	if (offset == ra->prev_page + 1) {
-		if (ra->serial_cnt <= (max * 2))
-			ra->serial_cnt++;
-	} else {
-		ra->average = (ra->average + ra->serial_cnt) / 2;
-		ra->serial_cnt = 1;
-	}
-	preoffset = ra->prev_page;
 	ra->prev_page = offset;
 
 	if (offset >= ra->start && offset <= (ra->start + ra->size)) {
@@ -406,12 +395,22 @@ page_cache_readahead(struct address_space *mapping, struct file_ra_state *ra,
 		 * page beyond the end.  Expand the next readahead size.
 		 */
 		ra->next_size += 2;
+
+		if (ra->currnt_wnd_hit <= (max * 2))
+			ra->currnt_wnd_hit++;
 	} else {
 		/*
 		 * A miss - lseek, pagefault, pread, etc.  Shrink the readahead
 		 * window.
 		 */
 		ra->next_size -= 2;
+
+		average = ra->average;
+		if (average < ra->currnt_wnd_hit) {
+			average++;
+		}
+		ra->average = (average + ra->currnt_wnd_hit) / 2;
+		ra->currnt_wnd_hit = 1;
 	}
 
 	if ((long)ra->next_size > (long)max)
@@ -457,18 +456,17 @@ do_io:
 		 * ahead window and get some I/O underway for the new
 		 * current window.
 		 */
-		if (!first_access && preoffset >= ra->start &&
-				preoffset < (ra->start + ra->size)) {
-			 /* Heuristic:  If 'n' pages were
-			  * accessed in the current window, there
-			  * is a high probability that around 'n' pages
-			  * shall be used in the next current window.
-			  *
-			  * To minimize lazy-readahead triggered
-			  * in the next current window, read in
-			  * an extra page.
+		if (!first_access) {
+			 /* Heuristic: there is a high probability
+			  * that around  ra->average number of
+			  * pages shall be accessed in the next
+			  * current window.
 			  */
-			ra->next_size = preoffset - ra->start + 2;
+			average = ra->average;
+			if (ra->currnt_wnd_hit > average)
+				average = (ra->currnt_wnd_hit + ra->average + 1) / 2;
+
+			ra->next_size = min(average , (unsigned long)max);
 		}
 		ra->start = offset;
 		ra->size = ra->next_size;
@@ -492,21 +490,19 @@ do_io:
 		 */
 		if (ra->ahead_start == 0) {
 			/*
-			 * if the average io-size is less than maximum
+			 * If the average io-size is more than maximum
 			 * readahead size of the file the io pattern is
 			 * sequential. Hence  bring in the readahead window
 			 * immediately.
-			 * Else the i/o pattern is random. Bring
-			 * in the readahead window only if the last page of
-			 * the current window is accessed (lazy readahead).
+			 * If the average io-size is less than maximum
+			 * readahead size of the file the io pattern is
+			 * random. Hence don't bother to readahead.
 			 */
-			unsigned long average = ra->average;
-
-			if (ra->serial_cnt > average)
-				average = (ra->serial_cnt + ra->average) / 2;
+			average = ra->average;
+			if (ra->currnt_wnd_hit > average)
+				average = (ra->currnt_wnd_hit + ra->average + 1) / 2;
 
-			if ((average >= max) || (offset == (ra->start +
-							ra->size - 1))) {
+			if (average > max) {
 				ra->ahead_start = ra->start + ra->size;
 				ra->ahead_size = ra->next_size;
 				actual = do_page_cache_readahead(mapping, filp,
@@ -552,6 +548,7 @@ void handle_ra_miss(struct address_space *mapping,
 				ra->size = max;
 				ra->ahead_start = 0;
 				ra->ahead_size = 0;
+				ra->average = max / 2;
 			}
 		}
 		ra->prev_page = offset;
@@ -574,6 +571,6 @@ unsigned long max_sane_readahead(unsigned long nr)
 	unsigned long inactive;
 	unsigned long free;
 
-	get_zone_counts(&active, &inactive, &free);
+	__get_zone_counts(&active, &inactive, &free, NODE_DATA(numa_node_id()));
 	return min(nr, (inactive + free) / 2);
 }