The patch titled
Subject: mm/page-writeback.c: print a warning if the vm dirtiness settings are illogical
has been added to the -mm tree. Its filename is
mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical.patch
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------------------------------------------------------
From: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: 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@xxxxxxxxx
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/sysctl/vm.txt | 7 +++++++
mm/page-writeback.c | 5 ++++-
2 files changed, 11 insertions(+), 1 deletion(-)
diff -puN Documentation/sysctl/vm.txt~mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical Documentation/sysctl/vm.txt
--- a/Documentation/sysctl/vm.txt~mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical
+++ a/Documentation/sysctl/vm.txt
@@ -157,6 +157,10 @@ Note: the minimum value allowed for dirt
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
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 -puN mm/page-writeback.c~mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical mm/page-writeback.c
--- a/mm/page-writeback.c~mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical
+++ a/mm/page-writeback.c
@@ -433,8 +433,11 @@ static void domain_dirty_limits(struct d
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;
_
Patches currently in -mm which might be from laoar.shao@xxxxxxxxx are
mm-print-a-warning-once-the-vm-dirtiness-settings-is-illogical.patch
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