mm/page-writeback: highmem_is_dirtyable option
Add vm.highmem_is_dirtyable toggle
A 32 bit machine with HIGHMEM64 enabled running DCC has an MMAPed file of
approximately 2Gb size which contains a hash format that is written
randomly by the dbclean process. On 2.6.16 this process took a few
minutes. With lowmem only accounting of dirty ratios, this takes about 12
hours of 100% disk IO, all random writes.
Include a toggle in /proc/sys/vm/highmem_is_dirtyable which can be set to 1 to
add the highmem back to the total available memory count.
[akpm@linux-foundation.org: Fix the CONFIG_DETECT_SOFTLOCKUP=y build]
Signed-off-by: Bron Gondwana <brong@fastmail.fm>
Cc: Ethan Solomita <solo@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: WU Fengguang <wfg@mail.ustc.edu.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 8137482..c689b60af 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -69,6 +69,12 @@
int dirty_background_ratio = 5;
/*
+ * free highmem will not be subtracted from the total free memory
+ * for calculating free ratios if vm_highmem_is_dirtyable is true
+ */
+int vm_highmem_is_dirtyable;
+
+/*
* The generator of dirty data starts writeback at this percentage
*/
int vm_dirty_ratio = 10;
@@ -287,7 +293,10 @@
x = global_page_state(NR_FREE_PAGES)
+ global_page_state(NR_INACTIVE)
+ global_page_state(NR_ACTIVE);
- x -= highmem_dirtyable_memory(x);
+
+ if (!vm_highmem_is_dirtyable)
+ x -= highmem_dirtyable_memory(x);
+
return x + 1; /* Ensure that we never return 0 */
}