Re: Let's talk about the elephant in the room - the Linux kernel's inability to gracefully handle low memory pressure

[Johannes Weiner]

On Wed, Aug 07, 2019 at 09:59:27AM +0200, Michal Hocko wrote:
> On Tue 06-08-19 18:01:50, Johannes Weiner wrote:
> > On Tue, Aug 06, 2019 at 09:27:05AM -0700, Suren Baghdasaryan wrote:
> [...]
> > > > > I'm not sure 10s is the perfect value here, but I do think the kernel
> > > > > should try to get out of such a state, where interacting with the
> > > > > system is impossible, within a reasonable amount of time.
> > > > >
> > > > > It could be a little too short for non-interactive number-crunching
> > > > > systems...
> > > >
> > > > Would it be possible to have a module with tunning knobs as parameters
> > > > and hook into the PSI infrastructure? People can play with the setting
> > > > to their need, we wouldn't really have think about the user visible API
> > > > for the tuning and this could be easily adopted as an opt-in mechanism
> > > > without a risk of regressions.
> > 
> > It's relatively easy to trigger a livelock that disables the entire
> > system for good, as a regular user. It's a little weird to make the
> > bug fix for that an opt-in with an extensive configuration interface.
> 
> Yes, I definitely do agree that this is a bug fix more than a
> feature. The thing is that we do not know what the proper default is for
> a wide variety of workloads so some way of configurability is needed
> (level and period).  If making this a module would require a lot of
> additional code then we need a kernel command line parameter at least.
> 
> A module would have a nice advantage that you can change your
> configuration without rebooting. The same can be achieved by a sysfs on
> the other hand.

That's reasonable. How about my initial patch, but behind a config
option and the level and period configurable?

---