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-rw-r--r--include/linux/writeback.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index e9d371b6053..b625073b80c 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -7,6 +7,27 @@
#include <linux/sched.h>
#include <linux/fs.h>
+/*
+ * The 1/16 region above the global dirty limit will be put to maximum pauses:
+ *
+ * (limit, limit + limit/DIRTY_MAXPAUSE_AREA)
+ *
+ * The 1/16 region above the max-pause region, dirty exceeded bdi's will be put
+ * to loops:
+ *
+ * (limit + limit/DIRTY_MAXPAUSE_AREA, limit + limit/DIRTY_PASSGOOD_AREA)
+ *
+ * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
+ * time) for the dirty pages to drop, unless written enough pages.
+ *
+ * The global dirty threshold is normally equal to the global dirty limit,
+ * except when the system suddenly allocates a lot of anonymous memory and
+ * knocks down the global dirty threshold quickly, in which case the global
+ * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
+ */
+#define DIRTY_MAXPAUSE_AREA 16
+#define DIRTY_PASSGOOD_AREA 8
+
struct backing_dev_info;
/*