From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 7803E6B004A for ; Wed, 1 Sep 2010 20:54:14 -0400 (EDT) Date: Wed, 1 Sep 2010 19:54:04 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH 2/3] mm: page allocator: Calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake In-Reply-To: Message-ID: References: <20100901203422.GA19519@csn.ul.ie> <20100902092628.D065.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Mel Gorman , Andrew Morton , Linux Kernel List , linux-mm@kvack.org, Rik van Riel , Johannes Weiner , Minchan Kim , KAMEZAWA Hiroyuki List-ID: On Wed, 1 Sep 2010, Christoph Lameter wrote: > The effect needs to be the same as retrieving a global or > zone ZVC counter. Which is currently implemented in the following way: > > static inline unsigned long zone_page_state(struct zone *zone, > enum zone_stat_item item) > { > long x = atomic_long_read(&zone->vm_stat[item]); > #ifdef CONFIG_SMP > if (x < 0) > x = 0; > #endif > return x; > } > Here is a patch that defined a snapshot function that works in the same way: Subject: Add a snapshot function for vm statistics Add a snapshot function that can more accurately determine the current value of a zone counter. Signed-off-by: Christoph Lameter Index: linux-2.6/include/linux/vmstat.h =================================================================== --- linux-2.6.orig/include/linux/vmstat.h 2010-09-01 19:45:23.506071189 -0500 +++ linux-2.6/include/linux/vmstat.h 2010-09-01 19:53:02.978979081 -0500 @@ -170,6 +170,28 @@ return x; } +/* + * More accurate version that also considers the currently pending + * deltas. For that we need to loop over all cpus to find the current + * deltas. There is no synchronization so the result cannot be + * exactly accurate either. + */ +static inline unsigned long zone_page_state_snapshot(struct zone *zone, + enum zone_stat_item item) +{ + int cpu; + long x = atomic_long_read(&zone->vm_stat[item]); + +#ifdef CONFIG_SMP + for_each_online_cpu(cpu) + x += per_cpu_ptr(zone->pageset, cpu)->vm_stat_diff[item]; + + if (x < 0) + x = 0; +#endif + return x; +} + extern unsigned long global_reclaimable_pages(void); extern unsigned long zone_reclaimable_pages(struct zone *zone); -- 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