From: Johannes Weiner Subject: [patch 1/4] mm: exclude reserved pages from dirtyable memory Date: Tue, 20 Sep 2011 15:45:12 +0200 Message-ID: <1316526315-16801-2-git-send-email-jweiner@redhat.com> References: <1316526315-16801-1-git-send-email-jweiner@redhat.com> Cc: Mel Gorman , Christoph Hellwig , Dave Chinner , Wu Fengguang , Jan Kara , Rik van Riel , Minchan Kim , Chris Mason , "Theodore Ts'o" , Andreas Dilger , xfs@oss.sgi.com, linux-btrfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Andrew Morton Return-path: In-Reply-To: <1316526315-16801-1-git-send-email-jweiner@redhat.com> Sender: owner-linux-mm@kvack.org List-Id: linux-ext4.vger.kernel.org The amount of dirtyable pages should not include the total number of free pages: there is a number of reserved pages that the page allocator and kswapd always try to keep free. The closer (reclaimable pages - dirty pages) is to the number of reserved pages, the more likely it becomes for reclaim to run into dirty pages: +----------+ --- | anon | | +----------+ | | | | | | -- dirty limit new -- flusher new | file | | | | | | | | | -- dirty limit old -- flusher old | | | +----------+ --- reclaim | reserved | +----------+ | kernel | +----------+ Not treating reserved pages as dirtyable on a global level is only a conceptual fix. In reality, dirty pages are not distributed equally across zones and reclaim runs into dirty pages on a regular basis. But it is important to get this right before tackling the problem on a per-zone level, where the distance between reclaim and the dirty pages is mostly much smaller in absolute numbers. Signed-off-by: Johannes Weiner --- include/linux/mmzone.h | 1 + mm/page-writeback.c | 8 +++++--- mm/page_alloc.c | 1 + 3 files changed, 7 insertions(+), 3 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 1ed4116..e28f8e0 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -316,6 +316,7 @@ struct zone { * sysctl_lowmem_reserve_ratio sysctl changes. */ unsigned long lowmem_reserve[MAX_NR_ZONES]; + unsigned long totalreserve_pages; #ifdef CONFIG_NUMA int node; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index da6d263..9f896db 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -169,8 +169,9 @@ static unsigned long highmem_dirtyable_memory(unsigned long total) struct zone *z = &NODE_DATA(node)->node_zones[ZONE_HIGHMEM]; - x += zone_page_state(z, NR_FREE_PAGES) + - zone_reclaimable_pages(z); + x += zone_page_state(z, NR_FREE_PAGES) - + zone->totalreserve_pages; + x += zone_reclaimable_pages(z); } /* * Make sure that the number of highmem pages is never larger @@ -194,7 +195,8 @@ static unsigned long determine_dirtyable_memory(void) { unsigned long x; - x = global_page_state(NR_FREE_PAGES) + global_reclaimable_pages(); + x = global_page_state(NR_FREE_PAGES) - totalreserve_pages; + x += global_reclaimable_pages(); if (!vm_highmem_is_dirtyable) x -= highmem_dirtyable_memory(x); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1dba05e..7e8e2ee 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5075,6 +5075,7 @@ static void calculate_totalreserve_pages(void) if (max > zone->present_pages) max = zone->present_pages; + zone->totalreserve_pages = max; reserve_pages += max; } } -- 1.7.6 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org