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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Minchan Kim <minchan.kim@gmail.com>
Subject: Re: [PATCH 3/3] reset wmark_min and inactive ratio of zone when hotplug happens
Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
       Mel Gorman <mel@csn.ul.ie>, Rik van Riel <riel@redhat.com>,
       Johannes Weiner <hannes@cmpxchg.org>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Yasunori Goto <y-goto@jp.fujitsu.com>
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Date: Wed, 20 May 2009 16:34:08 +0900 (JST)
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> This patch solve two problems.
> 
> Whenever memory hotplug sucessfully happens, zone->present_pages
> have to be changed.
> 
> 1) Now, memory hotplug calls setup_per_zone_wmark_min only when
> online_pages called, not offline_pages.
> 
> It breaks balance.
> 
> 2) If zone->present_pages is changed, we also have to change
> zone->inactive_ratio. That's because inactive_ratio depends
> on zone->present_pages.

Good catch!
looks good to me. but I'm not familiar this area. CC to Goto-san.





> CC: Mel Gorman <mel@csn.ul.ie>
> CC: Rik van Riel <riel@redhat.com>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> CC: Johannes Weiner <hannes@cmpxchg.org>
> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> ---
>  mm/memory_hotplug.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 40bf385..1611010 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -423,6 +423,7 @@ int online_pages(unsigned long pfn, unsigned long nr_pages)
>  	zone->zone_pgdat->node_present_pages += onlined_pages;
>  
>  	setup_per_zone_wmark_min();
> +	calculate_per_zone_inactive_ratio(zone);
>  	if (onlined_pages) {
>  		kswapd_run(zone_to_nid(zone));
>  		node_set_state(zone_to_nid(zone), N_HIGH_MEMORY);
> @@ -832,6 +833,9 @@ repeat:
>  	totalram_pages -= offlined_pages;
>  	num_physpages -= offlined_pages;
>  
> +	setup_per_zone_wmark_min();
> +	calculate_per_zone_inactive_ratio(zone);
> +
>  	vm_total_pages = nr_free_pagecache_pages();
>  	writeback_set_ratelimit();
>  
> -- 
> 1.5.4.3
> 
> 
> 
> -- 
> Kinds Regards
> Minchan Kim