On Fri, Apr 20, 2018 at 04:54:53PM -0400, Mikulas Patocka wrote: > On Fri, 20 Apr 2018, Michal Hocko wrote: > > No way. This is just wrong! First of all, you will explode most likely > > on many allocations of small sizes. Second, CONFIG_DEBUG_VM tends to be > > enabled quite often. > > You're an evil person who doesn't want to fix bugs. Steady on. There's no need for that. Michal isn't evil. Please apologise. > You refused to fix vmalloc(GFP_NOIO) misbehavior a year ago (did you make > some progress with it since that time?) and you refuse to fix kvmalloc > misuses. I understand you're frustrated, but this is not the way to get the problems fixed. > I tried this patch on text-only virtual machine and /proc/vmallocinfo > shows 614kB more memory. I tried it on a desktop machine with the chrome > browser open and /proc/vmallocinfo space is increased by 7MB. So no - this > won't exhaust memory and kill the machine. This is good data, thank you for providing it. > Arguing that this increases memory consumption is as bogus as arguing that > CONFIG_LOCKDEP increses memory consumption. No one is forcing you to > enable CONFIG_LOCKDEP and no one is forcing you to enable this kvmalloc > test too. I think there's a real problem which is that CONFIG_DEBUG_VM is too broad. It inserts code in a *lot* of places, some of which is quite expensive. We would do better to split it into more granular pieces ... although an explosion of configuration options isn't great either. Maybe just CONFIG_DEBUG_VM and CONFIG_DEBUG_VM_EXPENSIVE. Michal may be wrong, but he's not evil.
