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Commit 5fce25a9 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 546040dc

mm/page-writeback.c

+17 −2
Original line number Diff line number Diff line
@@ -355,8 +355,8 @@ get_dirty_limits(long *pbackground, long *pdirty, long *pbdi_dirty, 
 */

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;
@@ -376,11 +376,26 @@ static void balance_dirty_pages(struct address_space *mapping) 


		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)

			bdi->dirty_exceeded = 1;