From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: [PATCH 3/7] writeback: fix dirtied pages accounting on sub-page writes Date: Mon, 28 Nov 2011 21:53:41 +0800 Message-ID: <20111128140513.275099009@intel.com> References: <20111128135338.249672012@intel.com> Cc: Jan Kara , Peter Zijlstra , Wu Fengguang To: Return-path: Received: from mga03.intel.com ([143.182.124.21]:26312 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753330Ab1K1OJI (ORCPT ); Mon, 28 Nov 2011 09:09:08 -0500 CC: Christoph Hellwig cc: Andrew Morton Cc: LKML Content-Disposition: inline; filename=writeback-accurate-task-dirtied.patch Sender: linux-fsdevel-owner@vger.kernel.org List-ID: When dd in 512bytes, generic_perform_write() calls balance_dirty_pages_ratelimited() 8 times for the same page, but obviously the page is only dirtied once. Fix it by accounting tsk->nr_dirtied and bdp_ratelimits at page dirty time. Acked-by: Peter Zijlstra Signed-off-by: Wu Fengguang --- mm/page-writeback.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) --- linux-next.orig/mm/page-writeback.c 2011-11-28 21:23:20.000000000 +0800 +++ linux-next/mm/page-writeback.c 2011-11-28 21:23:23.000000000 +0800 @@ -1239,8 +1239,6 @@ void balance_dirty_pages_ratelimited_nr( if (bdi->dirty_exceeded) ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); - current->nr_dirtied += nr_pages_dirtied; - preempt_disable(); /* * This prevents one CPU to accumulate too many dirtied pages without @@ -1251,12 +1249,9 @@ void balance_dirty_pages_ratelimited_nr( p = &__get_cpu_var(bdp_ratelimits); if (unlikely(current->nr_dirtied >= ratelimit)) *p = 0; - else { - *p += nr_pages_dirtied; - if (unlikely(*p >= ratelimit_pages)) { - *p = 0; - ratelimit = 0; - } + else if (unlikely(*p >= ratelimit_pages)) { + *p = 0; + ratelimit = 0; } /* * Pick up the dirtied pages by the exited tasks. This avoids lots of @@ -1749,6 +1744,8 @@ void account_page_dirtied(struct page *p __inc_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); task_io_account_write(PAGE_CACHE_SIZE); + current->nr_dirtied++; + this_cpu_inc(bdp_ratelimits); } } EXPORT_SYMBOL(account_page_dirtied);