On Tue 07-07-20 09:04:36, Qian Cai wrote: > On Tue, Jul 07, 2020 at 02:06:19PM +0200, Michal Hocko wrote: > > On Tue 07-07-20 07:43:48, Qian Cai wrote: > > > > > > > > > > On Jul 7, 2020, at 6:28 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > > > > > Would you have any examples? Because I find this highly unlikely. > > > > OVERCOMMIT_NEVER only works when virtual memory is not largerly > > > > overcommited wrt to real memory demand. And that tends to be more of > > > > an exception rather than a rule. "Modern" userspace (whatever that > > > > means) tends to be really hungry with virtual memory which is only used > > > > very sparsely. > > > > > > > > I would argue that either somebody is running an "OVERCOMMIT_NEVER" > > > > friendly SW and this is a permanent setting or this is not used at all. > > > > At least this is my experience. > > > > > > > > So I strongly suspect that LTP test failure is not something we should > > > > really lose sleep over. It would be nice to find a way to flush existing > > > > batches but I would rather see a real workload that would suffer from > > > > this imprecision. > > > > > > I hear you many times that you really don’t care about those use > > > cases unless you hear exactly people are using in your world. > > > > > > For example, when you said LTP oom tests are totally artificial last > > > time and how less you care about if they are failing, and I could only > > > enjoy their efficiencies to find many issues like race conditions > > > and bad error accumulation handling etc that your “real world use > > > cases” are going to take ages or no way to flag them. > > > > Yes, they are effective at hitting corner cases and that is fine. I > > am not dismissing their usefulness. I have tried to explain that many > > times but let me try again. Seeing a corner case and think about a > > potential fix is one thing. On the other hand it is not really ideal to > > treat such a failure a hard regression and consider otherwise useful > > Well, terms like "corner cases" and "hard regression" are rather > subjective. Existing real life examples really makes them less subjective though. [...] > > LTP is a very useful tool to raise awareness of potential problems but > > you shouldn't really follow those results just blindly. > > You must think I am a newbie tester to give me this piece of advice > then. Not by even close. I can clearly see your involvement in testing and how many good bug reports that results in. -- Michal Hocko SUSE Labs
