Re: Balloon pressuring page cache

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>>>     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

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