Messages in this thread Patch in this message | | | 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 |
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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 <cl@linux.com>
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);
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