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From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@suse.de>, Andrew Morton <akpm@linux-foundation.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	Linux-FSDevel <linux-fsdevel@vger.kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 6/6] mm: page_alloc: Reduce cost of the fair zone allocation policy
Date: Fri, 08 Aug 2014 17:27:15 +0200	[thread overview]
Message-ID: <53E4EC53.1050904@suse.cz> (raw)
In-Reply-To: <1404893588-21371-7-git-send-email-mgorman@suse.de>

On 07/09/2014 10:13 AM, Mel Gorman wrote:
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1604,6 +1604,9 @@ again:
>  	}
>  
>  	__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));

This can underflow zero, right?

> +	if (zone_page_state(zone, NR_ALLOC_BATCH) == 0 &&

AFAICS, zone_page_state will correct negative values to zero only for
CONFIG_SMP. Won't this check be broken on !CONFIG_SMP?

I just stumbled upon this when trying to optimize the function. I didn't check
how rest of the design copes with negative NR_ALLOC_BATCH values.

> +	    !zone_is_fair_depleted(zone))
> +		zone_set_flag(zone, ZONE_FAIR_DEPLETED);
>  
>  	__count_zone_vm_events(PGALLOC, zone, 1 << order);
>  	zone_statistics(preferred_zone, zone, gfp_flags);
> @@ -1915,6 +1918,18 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
>  
>  #endif	/* CONFIG_NUMA */
>  


WARNING: multiple messages have this Message-ID (diff)
From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@suse.de>, Andrew Morton <akpm@linux-foundation.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	Linux-FSDevel <linux-fsdevel@vger.kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 6/6] mm: page_alloc: Reduce cost of the fair zone allocation policy
Date: Fri, 08 Aug 2014 17:27:15 +0200	[thread overview]
Message-ID: <53E4EC53.1050904@suse.cz> (raw)
In-Reply-To: <1404893588-21371-7-git-send-email-mgorman@suse.de>

On 07/09/2014 10:13 AM, Mel Gorman wrote:
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1604,6 +1604,9 @@ again:
>  	}
>  
>  	__mod_zone_page_state(zone, NR_ALLOC_BATCH, -(1 << order));

This can underflow zero, right?

> +	if (zone_page_state(zone, NR_ALLOC_BATCH) == 0 &&

AFAICS, zone_page_state will correct negative values to zero only for
CONFIG_SMP. Won't this check be broken on !CONFIG_SMP?

I just stumbled upon this when trying to optimize the function. I didn't check
how rest of the design copes with negative NR_ALLOC_BATCH values.

> +	    !zone_is_fair_depleted(zone))
> +		zone_set_flag(zone, ZONE_FAIR_DEPLETED);
>  
>  	__count_zone_vm_events(PGALLOC, zone, 1 << order);
>  	zone_statistics(preferred_zone, zone, gfp_flags);
> @@ -1915,6 +1918,18 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
>  
>  #endif	/* CONFIG_NUMA */
>  

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  parent reply	other threads:[~2014-08-08 15:27 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-07-09  8:13 [PATCH 0/5] Reduce sequential read overhead Mel Gorman
2014-07-09  8:13 ` Mel Gorman
2014-07-09  8:13 ` [PATCH 1/6] mm: pagemap: Avoid unnecessary overhead when tracepoints are deactivated Mel Gorman
2014-07-09  8:13   ` Mel Gorman
2014-07-10 12:01   ` Johannes Weiner
2014-07-10 12:01     ` Johannes Weiner
2014-07-09  8:13 ` [PATCH 2/6] mm: Rearrange zone fields into read-only, page alloc, statistics and page reclaim lines Mel Gorman
2014-07-09  8:13   ` Mel Gorman
2014-07-10 12:06   ` Johannes Weiner
2014-07-10 12:06     ` Johannes Weiner
2014-07-09  8:13 ` [PATCH 3/6] mm: Move zone->pages_scanned into a vmstat counter Mel Gorman
2014-07-09  8:13   ` Mel Gorman
2014-07-10 12:08   ` Johannes Weiner
2014-07-10 12:08     ` Johannes Weiner
2014-07-09  8:13 ` [PATCH 4/6] mm: vmscan: Only update per-cpu thresholds for online CPU Mel Gorman
2014-07-09  8:13   ` Mel Gorman
2014-07-10 12:09   ` Johannes Weiner
2014-07-10 12:09     ` Johannes Weiner
2014-07-09  8:13 ` [PATCH 5/6] mm: page_alloc: Abort fair zone allocation policy when remotes nodes are encountered Mel Gorman
2014-07-09  8:13   ` Mel Gorman
2014-07-10 12:14   ` Johannes Weiner
2014-07-10 12:14     ` Johannes Weiner
2014-07-10 12:44     ` Mel Gorman
2014-07-10 12:44       ` Mel Gorman
2014-07-09  8:13 ` [PATCH 6/6] mm: page_alloc: Reduce cost of the fair zone allocation policy Mel Gorman
2014-07-09  8:13   ` Mel Gorman
2014-07-10 12:18   ` Johannes Weiner
2014-07-10 12:18     ` Johannes Weiner
2014-08-08 15:27   ` Vlastimil Babka [this message]
2014-08-08 15:27     ` Vlastimil Babka
2014-08-11 12:12     ` Mel Gorman
2014-08-11 12:12       ` Mel Gorman
2014-08-11 12:34       ` Vlastimil Babka
2014-08-11 12:34         ` Vlastimil Babka
2014-09-02 14:01         ` Johannes Weiner
2014-09-02 14:01           ` Johannes Weiner
2014-09-05 10:14           ` [PATCH] mm: page_alloc: Fix setting of ZONE_FAIR_DEPLETED on UP Mel Gorman
2014-09-05 10:14             ` Mel Gorman
2014-09-07  6:32             ` Leon Romanovsky
2014-09-07  6:32               ` Leon Romanovsky
2014-09-08 11:57               ` [PATCH] mm: page_alloc: Fix setting of ZONE_FAIR_DEPLETED on UP v2 Mel Gorman
2014-09-08 11:57                 ` Mel Gorman
2014-09-09  8:17                 ` Leon Romanovsky
2014-09-09 19:53                 ` Andrew Morton
2014-09-09 19:53                   ` Andrew Morton
2014-09-10  9:16                   ` Mel Gorman
2014-09-10  9:16                     ` Mel Gorman
2014-09-10 20:32                     ` Johannes Weiner
2014-09-10 20:32                       ` Johannes Weiner

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