Hello,
We've seen a significant perf degradation when reading a tmpfs file swapped into zram between 5.10 and 5.15. The source of the issue is:
* aa48e47e3906: memcg: infrastructure to flush memcg stats
There's a couple of commits that helps to bridge the gap in 5.16:
* 11192d9c124d: memcg: flush stats only if updated * fd25a9e0e23b: memcg: unify memcg stat flushing
Both of these apply cleanly and Shakeel (the author) has okayed the backport from his end. He also suggested backporting the following:
* 5b3be698a872: memcg: better bounds on the memcg stats updates
I personally did not test this one, but it applies cleanly, so there's probably no harm. I cc'd Shakeel in case you want confirmation on that. It's not a part of any tag yet.
Please backport all three (or at least the first two) to 5.15 LTS.
Thanks!