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; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
