>>> It's not about dangers as such. It's just that when linux hits OOM >>> all kind of error paths are being hit, latent bugs start triggering, >>> latency goes up drastically. >> Doesn't this suggest that the shrinker is preferable to the OOM >> notifier in the case that we're actually OOMing (with DEFLATE_ON_OOM)? > > I think it all depends on the use case. For the use case you > describe going to the shrinker might be preferable as you are > wanting to exert just a light bit of pressure to start some page > cache reclaim. However if you are wanting to make the deflation a > last resort sort of thing then I would think the OOM would make more > sense. Long story short: What you actually want is free page reporting combined with a) avoiding the guest page cache (emulated nvdimms, virtio-pmem). Not always possible and has some issues in non-trusted environments (IOW, cloud). b) a way to tame the page cache (e.g., drop it completely similar to drop_caches, or a way to drop a specific fraction, things not touch for the last $SECONDS) etc. There are some nice discussions in response to Alexander's v16.1 posting. -- Thanks, David / dhildenb
