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>
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@ -157,6 +157,10 @@ Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any
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value lower than this limit will be ignored and the old configuration will be
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retained.
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Note: the value of dirty_bytes also must be set greater than
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dirty_background_bytes or the amount of memory corresponding to
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dirty_background_ratio.
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==============================================================
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dirty_expire_centisecs
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@ -176,6 +180,9 @@ generating disk writes will itself start writing out dirty data.
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The total available memory is not equal to total system memory.
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Note: dirty_ratio must be set greater than dirty_background_ratio or
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ratio corresponding to dirty_background_bytes.
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==============================================================
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dirty_writeback_centisecs
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@ -433,8 +433,11 @@ static void domain_dirty_limits(struct dirty_throttle_control *dtc)
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else
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bg_thresh = (bg_ratio * available_memory) / PAGE_SIZE;
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if (bg_thresh >= thresh)
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if (unlikely(bg_thresh >= thresh)) {
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pr_warn("vm direct limit must be set greater than background limit.\n");
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bg_thresh = thresh / 2;
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}
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tsk = current;
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if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
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bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32;
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