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SubjectRe: [patch 00/19] VM pageout scalability improvements
* Rik van Riel <riel@redhat.com> [2008-01-08 15:59:39]:

> On large memory systems, the VM can spend way too much time scanning
> through pages that it cannot (or should not) evict from memory. Not
> only does it use up CPU time, but it also provokes lock contention
> and can leave large systems under memory presure in a catatonic state.
>
> Against 2.6.24-rc6-mm1
>
> This patch series improves VM scalability by:
>
> 1) making the locking a little more scalable
>
> 2) putting filesystem backed, swap backed and non-reclaimable pages
> onto their own LRUs, so the system only scans the pages that it
> can/should evict from memory
>
> 3) switching to SEQ replacement for the anonymous LRUs, so the
> number of pages that need to be scanned when the system
> starts swapping is bound to a reasonable number
>
> More info on the overall design can be found at:
>
> http://linux-mm.org/PageReplacementDesign
>
>
> Changelog:
> - merge memcontroller split LRU code into the main split LRU patch,
> since it is not functionally different (it was split up only to help
> people who had seen the last version of the patch series review it)
> - drop the page_file_cache debugging patch, since it never triggered
> - reintroduce code to not scan anon list if swap is full
> - add code to scan anon list if page cache is very small already
> - use lumpy reclaim more aggressively for smaller order > 1 allocations
>

Hi, Rik,

I've just started the patch series, the compile fails for me on a
powerpc box. global_lru_pages() is defined under CONFIG_PM, but used
else where in mm/page-writeback.c. None of the global_lru_pages()
parameters depend on CONFIG_PM. Here's a simple patch to fix it.

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b14e188..39e6aef 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1920,6 +1920,14 @@ void wakeup_kswapd(struct zone *zone, int order)
wake_up_interruptible(&pgdat->kswapd_wait);
}

+unsigned long global_lru_pages(void)
+{
+ return global_page_state(NR_ACTIVE_ANON)
+ + global_page_state(NR_ACTIVE_FILE)
+ + global_page_state(NR_INACTIVE_ANON)
+ + global_page_state(NR_INACTIVE_FILE);
+}
+
#ifdef CONFIG_PM
/*
* Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages
@@ -1968,14 +1976,6 @@ static unsigned long shrink_all_zones(unsigned long nr_pages, int prio,
return ret;
}

-unsigned long global_lru_pages(void)
-{
- return global_page_state(NR_ACTIVE_ANON)
- + global_page_state(NR_ACTIVE_FILE)
- + global_page_state(NR_INACTIVE_ANON)
- + global_page_state(NR_INACTIVE_FILE);
-}
-
/*
* Try to free `nr_pages' of memory, system-wide, and return the number of
* freed pages.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL


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