quoted

quoted

    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