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authorYafang Shao <laoar.shao@gmail.com>2017-11-15 17:33:45 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-15 18:21:03 -0800
commit0f6d24f878568fac579a1962d0bf7cb9f01e0ceb (patch)
tree5fa7529b42621ab7b1a86ec8d5f3dc01cb9d7b10
parent66e8b438bd5c75498cfe915c4219049eaebcb869 (diff)
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mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical
The vm direct limit setting must be set greater than vm background limit setting. Otherwise print a warning to help the operator to figure out that the vm dirtiness settings is in illogical state. Link: http://lkml.kernel.org/r/1506592464-30962-1-git-send-email-laoar.shao@gmail.com Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Cc: Jan Kara <jack@suse.cz> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/sysctl/vm.txt7
-rw-r--r--mm/page-writeback.c5
2 files changed, 11 insertions, 1 deletions
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 9baf66a9ef4e..30fd16b14196 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -157,6 +157,10 @@ Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any
value lower than this limit will be ignored and the old configuration will be
retained.
+Note: the value of dirty_bytes also must be set greater than
+dirty_background_bytes or the amount of memory corresponding to
+dirty_background_ratio.
+
==============================================================
dirty_expire_centisecs
@@ -176,6 +180,9 @@ generating disk writes will itself start writing out dirty data.
The total available memory is not equal to total system memory.
+Note: dirty_ratio must be set greater than dirty_background_ratio or
+ratio corresponding to dirty_background_bytes.
+
==============================================================
dirty_writeback_centisecs
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 76a43c17761b..768fe4e37e6a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -433,8 +433,11 @@ static void domain_dirty_limits(struct dirty_throttle_control *dtc)
else
bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE;
- if (bg_thresh >= thresh)
+ if (unlikely(bg_thresh >= thresh)) {
+ pr_warn("vm direct limit must be set greater than background limit.\n");
bg_thresh = thresh / 2;
+ }
+
tsk = current;
if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32;