From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 71AB56B0005 for ; Thu, 14 Jul 2016 11:22:27 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id o80so58722681wme.1 for ; Thu, 14 Jul 2016 08:22:27 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o64si34413421wmb.29.2016.07.14.08.22.26 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 14 Jul 2016 08:22:26 -0700 (PDT) Subject: Re: [PATCH 3/4] mm, page_alloc: fix dirtyable highmem calculation References: <1468404004-5085-1-git-send-email-mgorman@techsingularity.net> <1468404004-5085-4-git-send-email-mgorman@techsingularity.net> From: Vlastimil Babka Message-ID: <1e5938cd-0e03-6cb9-4d5f-fee94fc1479e@suse.cz> Date: Thu, 14 Jul 2016 17:22:25 +0200 MIME-Version: 1.0 In-Reply-To: <1468404004-5085-4-git-send-email-mgorman@techsingularity.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman , Andrew Morton , Linux-MM Cc: Johannes Weiner , Minchan Kim , LKML On 07/13/2016 12:00 PM, Mel Gorman wrote: > From: Minchan Kim > > Note from Mel: This may optionally be considered a fix to the mmotm patch > mm-page_alloc-consider-dirtyable-memory-in-terms-of-nodes.patch > but if so, please preserve credit for Minchan. > > When I tested vmscale in mmtest in 32bit, I found the benchmark was slow > down 0.5 times. > > base node > 1 global-1 > User 12.98 16.04 > System 147.61 166.42 > Elapsed 26.48 38.08 > > With vmstat, I found IO wait avg is much increased compared to base. > > The reason was highmem_dirtyable_memory accumulates free pages and > highmem_file_pages from HIGHMEM to MOVABLE zones which was wrong. With > that, dirth_thresh in throtlle_vm_write is always 0 so that it calls > congestion_wait frequently if writeback starts. > > With this patch, it is much recovered. > > base node fi > 1 global-1 fix > User 12.98 16.04 13.78 > System 147.61 166.42 143.92 > Elapsed 26.48 38.08 29.64 > > Signed-off-by: Minchan Kim > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Just some nitpicks: > --- > mm/page-writeback.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 0bca2376bd42..7b41d1290783 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -307,27 +307,31 @@ static unsigned long highmem_dirtyable_memory(unsigned long total) > { > #ifdef CONFIG_HIGHMEM > int node; > - unsigned long x = 0; > + unsigned long x; > int i; > - unsigned long dirtyable = atomic_read(&highmem_file_pages); > + unsigned long dirtyable = 0; This wasn't necessary? > > for_each_node_state(node, N_HIGH_MEMORY) { > for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { > struct zone *z; > + unsigned long nr_pages; > > if (!is_highmem_idx(i)) > continue; > > z = &NODE_DATA(node)->node_zones[i]; > - dirtyable += zone_page_state(z, NR_FREE_PAGES); > + if (!populated_zone(z)) > + continue; > > + nr_pages = zone_page_state(z, NR_FREE_PAGES); > /* watch for underflows */ > - dirtyable -= min(dirtyable, high_wmark_pages(z)); > - > - x += dirtyable; > + nr_pages -= min(nr_pages, high_wmark_pages(z)); > + dirtyable += nr_pages; > } > } > > + x = dirtyable + atomic_read(&highmem_file_pages); And then this addition wouldn't be necessary. BTW I think we could also ditch the "x" variable and just use the "dirtyable" for the rest of the function. > + > /* > * Unreclaimable memory (kernel memory or anonymous memory > * without swap) can bring down the dirtyable pages below > -- 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/ . Don't email: email@kvack.org