Hi Hugh, On 05/11/2012 11:10 PM, Hugh Dickins wrote: > On Fri, 11 May 2012, Minchan Kim wrote: >> On 05/11/2012 05:30 PM, Sasha Levin wrote: >> >>>> Commit 93278814d359 "mm: fix division by 0 in percpu_pagelist_fraction()" >>>> mistakenly initialized percpu_pagelist_fraction to the sysctl's minimum 8, >>>> which leaves 1/8th of memory on percpu lists (on each cpu??); but most of >>>> us expect it to be left unset at 0 (and it's not then used as a divisor). >>> >>> I'm a bit confused about this, does it mean that once you set >>> percpu_pagelist_fraction to a value above the minimum, you can no >>> longer set it back to being 0? >> >> >> Unfortunately, Yes. :( >> It's rather awkward and need fix. > > It's inelegant, but does that actually need a fix? Has anybody asked > for that option in the six years of percpu_pagelist_fraction? I don't have heard about it but thing we can't reset to 0 again once we set some number to above 8 is very strange. Sometime, someone may raise the value on /proc/sys/vm/percpu_pagelist_fraction to test it and realized function of the knob so he want to reset it to 0 default value, again. But he couldn't. It's very strange. :( > > Does setting percpu_pagelist_fraction to some large number perhaps > approximate to the default behaviour of percpu_pagelist_fraction 0? Yes. But it's not intuitive. > > I don't care very much either way - just don't want this discussion > to divert from applying last night's fix to the default behaviour > that most people expect. Of course. It's totally from my careless review. Actually, I didn't find to change default value to 8 when I review the patch. I just focused on proc_dointvec_minmax's err return value. Shame on me. :( Thanks for spot it. > > Hugh > > -- > 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/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> > -- Kind regards, Minchan Kim -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>