linux-kernel - Re: [PATCH 3/4] mm/hotplug: free zone->pageset when a zone becomes empty

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Message-ID: <50178C9B.8090408@cn.fujitsu.com>
Date:	Tue, 31 Jul 2012 15:43:23 +0800
From:	Wen Congyang <wency@...fujitsu.com>
To:	Jiang Liu <jiang.liu@...wei.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Yinghai Lu <yinghai@...nel.org>,
	Tony Luck <tony.luck@...el.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Keping Chen <chenkeping@...wei.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Jiang Liu <liuj97@...il.com>,
	Wei Wang <Bessel.Wang@...wei.com>
Subject: Re: [PATCH 3/4] mm/hotplug: free zone->pageset when a zone becomes
 empty

At 07/05/2012 05:45 PM, Jiang Liu Wrote:
> When a zone becomes empty after memory offlining, free zone->pageset.
> Otherwise it will cause memory leak when adding memory to the empty
> zone again because build_all_zonelists() will allocate zone->pageset
> for an empty zone.
> 
> Signed-off-by: Jiang Liu <liuj97@...il.com>
> Signed-off-by: Wei Wang <Bessel.Wang@...wei.com>
> ---
>  include/linux/mm.h  |    1 +
>  mm/memory_hotplug.c |    3 +++
>  mm/page_alloc.c     |   13 +++++++++++++
>  3 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index b36d08c..f8b62f2 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1331,6 +1331,7 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...);
>  extern void setup_per_cpu_pageset(void);
>  
>  extern void zone_pcp_update(struct zone *zone);
> +extern void zone_pcp_reset(struct zone *zone);
>  
>  /* nommu.c */
>  extern atomic_long_t mmap_pages_allocated;
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index bce80c7..998b792 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -966,6 +966,9 @@ repeat:
>  
>  	init_per_zone_wmark_min();
>  
> +	if (!populated_zone(zone))
> +		zone_pcp_reset(zone);
> +
>  	if (!node_present_pages(node)) {
>  		node_clear_state(node, N_HIGH_MEMORY);
>  		kswapd_stop(node);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index ebf319d..5964b7a 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5872,6 +5872,19 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
>  #endif
>  
>  #ifdef CONFIG_MEMORY_HOTREMOVE
> +void zone_pcp_reset(struct zone *zone)
> +{
> +	unsigned long flags;
> +
> +	/* avoid races with drain_pages()  */
> +	local_irq_save(flags);

drain_pages() may run on another cpu, so it cann't avoid
races with drain_pages().

Thanks
Wen Congyang

> +	if (zone->pageset != &boot_pageset) {
> +		free_percpu(zone->pageset);
> +		zone->pageset = &boot_pageset;
> +	}
> +	local_irq_restore(flags);
> +}
> +
>  /*
>   * All pages in the range must be isolated before calling this.
>   */

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