On Fri, 22 Sep 2017 07:12:32 +0800 Yafang Shao <laoar.shao@xxxxxxxxx> wrote: > 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@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
