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mm/page-writeback.c: do not count anon pages as dirtyable memory

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commit a1c3bfb2f67ef766de03f1f56bdfff9c8595ab14 upstream.

The VM is currently heavily tuned to avoid swapping.  Whether that is
good or bad is a separate discussion, but as long as the VM won't swap
to make room for dirty cache, we can not consider anonymous pages when
calculating the amount of dirtyable memory, the baseline to which
dirty_background_ratio and dirty_ratio are applied.

A simple workload that occupies a significant size (40+%, depending on
memory layout, storage speeds etc.) of memory with anon/tmpfs pages and
uses the remainder for a streaming writer demonstrates this problem.  In
that case, the actual cache pages are a small fraction of what is
considered dirtyable overall, which results in an relatively large
portion of the cache pages to be dirtied.  As kswapd starts rotating
these, random tasks enter direct reclaim and stall on IO.

Only consider free pages and file pages dirtyable.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Tejun Heo <tj@kernel.org>
Tested-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johannes Weiner
2014-01-29 14:05:41 -08:00
committed by Greg Kroah-Hartman
parent 03381bd289
commit 4852614996
3 changed files with 18 additions and 40 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/vmstat.h
-3
View File
@@ -142,9 +142,6 @@ static inline unsigned long zone_page_state_snapshot(struct zone *zone,
return x;
}
extern unsigned long global_reclaimable_pages(void);
extern unsigned long zone_reclaimable_pages(struct zone *zone);
#ifdef CONFIG_NUMA
/*
* Determine the per node value of a stat item. This function
mm/page-writeback.c
+4 -2
View File
@@ -202,7 +202,8 @@ static unsigned long zone_dirtyable_memory(struct zone *zone)
nr_pages = zone_page_state(zone, NR_FREE_PAGES);
nr_pages -= min(nr_pages, zone->dirty_balance_reserve);
nr_pages += zone_reclaimable_pages(zone);
nr_pages += zone_page_state(zone, NR_INACTIVE_FILE);
nr_pages += zone_page_state(zone, NR_ACTIVE_FILE);
return nr_pages;
}
@@ -255,7 +256,8 @@ static unsigned long global_dirtyable_memory(void)
x = global_page_state(NR_FREE_PAGES);
x -= min(x, dirty_balance_reserve);
x += global_reclaimable_pages();
x += global_page_state(NR_INACTIVE_FILE);
x += global_page_state(NR_ACTIVE_FILE);
if (!vm_highmem_is_dirtyable)
x -= highmem_dirtyable_memory(x);
mm/vmscan.c
+14 -35
View File
@@ -2117,6 +2117,20 @@ static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
return aborted_reclaim;
}
static unsigned long zone_reclaimable_pages(struct zone *zone)
{
int nr;
nr = zone_page_state(zone, NR_ACTIVE_FILE) +
zone_page_state(zone, NR_INACTIVE_FILE);
if (get_nr_swap_pages() > 0)
nr += zone_page_state(zone, NR_ACTIVE_ANON) +
zone_page_state(zone, NR_INACTIVE_ANON);
return nr;
}
static bool zone_reclaimable(struct zone *zone)
{
return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
@@ -3075,41 +3089,6 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
wake_up_interruptible(&pgdat->kswapd_wait);
}
/*
* The reclaimable count would be mostly accurate.
* The less reclaimable pages may be
* - mlocked pages, which will be moved to unevictable list when encountered
* - mapped pages, which may require several travels to be reclaimed
* - dirty pages, which is not "instantly" reclaimable
*/
unsigned long global_reclaimable_pages(void)
{
int nr;
nr = global_page_state(NR_ACTIVE_FILE) +
global_page_state(NR_INACTIVE_FILE);
if (get_nr_swap_pages() > 0)
nr += global_page_state(NR_ACTIVE_ANON) +
global_page_state(NR_INACTIVE_ANON);
return nr;
}
unsigned long zone_reclaimable_pages(struct zone *zone)
{
int nr;
nr = zone_page_state(zone, NR_ACTIVE_FILE) +
zone_page_state(zone, NR_INACTIVE_FILE);
if (get_nr_swap_pages() > 0)
nr += zone_page_state(zone, NR_ACTIVE_ANON) +
zone_page_state(zone, NR_INACTIVE_ANON);
return nr;
}
#ifdef CONFIG_HIBERNATION
/*
* Try to free `nr_to_reclaim' of memory, system-wide, and return the number of