[REGESSION] systemd-oomd overreacting due to PSI changes for Btrfs (was: Re: [PATCH 3/5] btrfs: add manual PSI accounting for compressed reads)

[Christoph Hellwig]

On Thu, Nov 03, 2022 at 11:46:52AM +0100, Thorsten Leemhuis wrote:
> It seems this patch makes systemd-oomd overreact on my day-to-day
> machine and aggressively kill applications. I'm not the only one that
> noticed such a behavior with 6.1 pre-releases:
> https://bugzilla.redhat.com/show_bug.cgi?id=2133829
> https://bugzilla.redhat.com/show_bug.cgi?id=2134971
> 
> I think I have a pretty reliable way to trigger the issue that involves
> starting the apps that I normally use and a VM that I occasionally use,
> which up to now never resulted in such a behaviour.
> 
> On master as of today (8e5423e991e8) I can trigger the problem within a
> minute or two. But I fail to trigger it with v6.0.6 or when I revert
> 4088a47e78f9 ("btrfs: add manual PSI accounting for compressed reads").
> And yes, I use btrfs with compression for / and /home/.

So, I did in fact not want to include this patch because it is a little
iffy and includes PSI accounting for reads where btrfs just does
aggresive readaround for compression, but Johannes asked for it to be
added.  I'd be perfectly fine with just reverting it.