Re: [PATCH v4] mm: introduce validity check on vm dirtiness settings
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2017-09-26 23:59:53
On Fri, 22 Sep 2017 07:12:32 +0800 Yafang Shao [off-list ref] wrote:
quoted hunk ↗ jump to hunk
we can find the logic in domain_dirty_limits() that when dirty bg_thresh is bigger than dirty thresh, bg_thresh will be set as thresh * 1 / 2. if (bg_thresh >= thresh) bg_thresh = thresh / 2; But actually we can set vm background dirtiness bigger than vm dirtiness successfully. This behavior may mislead us. We'd better do this validity check at the beginning. ...--- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt@@ -156,6 +156,9 @@ read. 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 cannot be set lower than +dirty_background_bytes or the amount of memory corresponding to +dirty_background_ratio.
I think this means that a script which alters both dirty_bytes and dirty_background_bytes must alter dirty_background_bytes first if they are being decreased and must alter dirty_bytes first if they are being increased. Or something like that. And existing scripts which do not do this will cease to work correctly, no? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>