On Thu 02-09-21 12:55:01, Andrew Morton wrote: > On Fri, 16 Jul 2021 07:25:47 -0500 Corey Minyard <cminyard@xxxxxxxxxx> wrote: > > > On Fri, Jul 16, 2021 at 07:19:24AM +0200, Michal Hocko wrote: > > > On Thu 01-07-21 07:54:30, minyard@xxxxxxx wrote: > > > > From: Corey Minyard <cminyard@xxxxxxxxxx> > > > > > > > > If you have a process with less than 1000 totalpages, the calculation: > > > > > > > > adj = (long)p->signal->oom_score_adj; > > > > ... > > > > adj *= totalpages / 1000; > > > > > > > > will always result in adj being zero no matter what oom_score_adj is, > > > > which could result in the wrong process being picked for killing. > > > > > > > > Fix by adding 1000 to totalpages before dividing. > > > > > > Yes, this is a known limitation of the oom_score_adj and its scale. > > > Is this a practical problem to be solved though? I mean 0-1000 pages is > > > not really that much different from imprecision at a larger scale where > > > tasks are effectively considered equal. > > > > Known limitation? Is this documented? I couldn't find anything that > > said "oom_score_adj doesn't work at all with programs with <1000 pages > > besides setting the value to -1000". > > > > > > > > I have to say I do not really like the proposed workaround. It doesn't > > > really solve the problem yet it adds another special case. > > > > The problem is that if you have a small program, there is no way to > > set it's priority besides completely disablling the OOM killer for > > it. > > > > I don't understand the special case comment. How is this adding a > > special case? This patch removes a special case. Small programs > > working different than big programs is a special case. Making them all > > work the same is removing an element of surprise from someone expecting > > things to work as documented. > > > > Can we please get this resolved one way or the other? As I've already said, I do not see this practical enough problem to warrant special treatment. Do we really care about controlling the oom behavior for tasks with <4MB of memory? I fully agree that the current situation is not ideal. The whole oom_score* API sucks but here we are with an user API that is effectivelly impossible to fix properly. -- Michal Hocko SUSE Labs
