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

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index e4b948080d20e7a537c7a83da17b8b5b7fec0008..a67b384157689ec9fda2abfec0173122fc98a4a8 100644 (file)
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -142,8 +142,6 @@ static inline unsigned long zone_page_state_snapshot(struct zone *zone,
        return x;
 }
 
-extern unsigned long global_reclaimable_pages(void);
-
 #ifdef CONFIG_NUMA
 /*
  * Determine the per node value of a stat item. This function

diff --git a/mm/internal.h b/mm/internal.h
index 612c14f5e0f570159fcf775991e88615fca26606..29e1e761f9ebe3fee42eea1b0e77589122a23d24 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -83,7 +83,6 @@ extern unsigned long highest_memmap_pfn;
  */
 extern int isolate_lru_page(struct page *page);
 extern void putback_lru_page(struct page *page);
-extern unsigned long zone_reclaimable_pages(struct zone *zone);
 extern bool zone_reclaimable(struct zone *zone);
 
 /*

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 61119b8a11e6d37bb90a6446dd4b44c7c408c161..2d30e2cfe8047606064f117fbaca4675540e00dd 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -205,7 +205,8 @@ 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;
 }
@@ -258,7 +259,8 @@ 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);

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 90c4075d8d75af6358ba6c789bc0747f53460a4d..a9c74b409681a460f2c2ef5f45b3f2283a81a4b8 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -147,7 +147,7 @@ static bool global_reclaim(struct scan_control *sc)
 }
 #endif
 
-unsigned long zone_reclaimable_pages(struct zone *zone)
+static unsigned long zone_reclaimable_pages(struct zone *zone)
 {
        int nr;
 
@@ -3315,27 +3315,6 @@ 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;
-}
-
 #ifdef CONFIG_HIBERNATION
 /*
  * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of