mm: speed up writeback ramp-up on clean systems

We allow violation of bdi limits if there is a lot of room on the system. Once we hit half the total limit we start enforcing bdi limits and bdi ramp-up should happen. Doing it this way avoids many small writeouts on an otherwise idle system and should also speed up the ramp-up. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by: Fengguang Wu <wfg@mail.ustc.edu.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm: speed up writeback ramp-up on clean systems
We allow violation of bdi limits if there is a lot of room on the system. Once we hit half the total limit we start enforcing bdi limits and bdi ramp-up should happen. Doing it this way avoids many small writeouts on an otherwise idle system and should also speed up the ramp-up. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by: Fengguang Wu <wfg@mail.ustc.edu.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Peter Zijlstra · Linus Torvalds
1 parent 546040dc48
Showing 1 changed file with 17 additions and 2 deletions Side-by-side Diff
mm/page-writeback.c
@@ -355,8 +355,8 @@
  */
 static void balance_dirty_pages(struct address_space *mapping)
 {
-	long bdi_nr_reclaimable;
-	long bdi_nr_writeback;
+	long nr_reclaimable, bdi_nr_reclaimable;
+	long nr_writeback, bdi_nr_writeback;
 	long background_thresh;
 	long dirty_thresh;
 	long bdi_thresh;
  
  
@@ -376,9 +376,24 @@
  
 		get_dirty_limits(&background_thresh, &dirty_thresh,
 				&bdi_thresh, bdi);
+
+		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+					global_page_state(NR_UNSTABLE_NFS);
+		nr_writeback = global_page_state(NR_WRITEBACK);
+
 		bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
 		bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+
 		if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
+			break;
+
+		/*
+		 * Throttle it only when the background writeback cannot
+		 * catch-up. This avoids (excessively) small writeouts
+		 * when the bdi limits are ramping up.
+		 */
+		if (nr_reclaimable + nr_writeback <
+				(background_thresh + dirty_thresh) / 2)
 			break;
  
 		if (!bdi->dirty_exceeded)
...	...	@@ -355,8 +355,8 @@
355	355	*/
356	356	static void balance_dirty_pages(struct address_space *mapping)
357	357	{
358		- long bdi_nr_reclaimable;
359		- long bdi_nr_writeback;
	358	+ long nr_reclaimable, bdi_nr_reclaimable;
	359	+ long nr_writeback, bdi_nr_writeback;
360	360	long background_thresh;
361	361	long dirty_thresh;
362	362	long bdi_thresh;
363	363
364	364
...	...	@@ -376,9 +376,24 @@
376	376
377	377	get_dirty_limits(&background_thresh, &dirty_thresh,
378	378	&bdi_thresh, bdi);
	379	+
	380	+ nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
	381	+ global_page_state(NR_UNSTABLE_NFS);
	382	+ nr_writeback = global_page_state(NR_WRITEBACK);
	383	+
379	384	bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
380	385	bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
	386	+
381	387	if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
	388	+ break;
	389	+
	390	+ /*
	391	+ * Throttle it only when the background writeback cannot
	392	+ * catch-up. This avoids (excessively) small writeouts
	393	+ * when the bdi limits are ramping up.
	394	+ */
	395	+ if (nr_reclaimable + nr_writeback <
	396	+ (background_thresh + dirty_thresh) / 2)
382	397	break;
383	398
384	399	if (!bdi->dirty_exceeded)