Re: [PATCH 0/1] Add swappiness argument to memory.reclaim

[Shakeel Butt <shakeelb@google.com>]

On Thu, Nov 30, 2023 at 07:36:53AM -0800, Dan Schatzberg wrote:
> (Sorry for the resend - forgot to cc the mailing lists)
> 
> This patch proposes augmenting the memory.reclaim interface with a
> swappiness=<val> argument that overrides the swappiness value for that instance
> of proactive reclaim.
> 
> Userspace proactive reclaimers use the memory.reclaim interface to trigger
> reclaim. The memory.reclaim interface does not allow for any way to effect the
> balance of file vs anon during proactive reclaim. The only approach is to adjust
> the vm.swappiness setting. However, there are a few reasons we look to control
> the balance of file vs anon during proactive reclaim, separately from reactive
> reclaim:
> 
> * Swapout should be limited to manage SSD write endurance. In near-OOM

Is this about swapout to SSD only?

>   situations we are fine with lots of swap-out to avoid OOMs. As these are
>   typically rare events, they have relatively little impact on write endurance.
>   However, proactive reclaim runs continuously and so its impact on SSD write
>   endurance is more significant. Therefore it is desireable to control swap-out
>   for proactive reclaim separately from reactive reclaim

This is understandable but swapout to zswap should be fine, right?
(Sorry I am not following the discussion on zswap patches from Nhat. Is
the answer there?)