Re: [PATCH 1/1] mm: add swapiness= arg to memory.reclaim

[Andrew Morton]

On Thu, 30 Nov 2023 07:36:54 -0800 Dan Schatzberg <schatzberg.dan@xxxxxxxxx> wrote:

> Allow proactive reclaimers to submit an additional swappiness=<val>
> argument to memory.reclaim. This overrides the global or per-memcg
> swappiness setting for that reclaim attempt.
> 
> For example:
> 
> echo "2M swappiness=0" > /sys/fs/cgroup/memory.reclaim
> 
> will perform reclaim on the rootcg with a swappiness setting of 0 (no
> swap) regardless of the vm.swappiness sysctl setting.
> 
> Signed-off-by: Dan Schatzberg <schatzberg.dan@xxxxxxxxx>
> ---
>  include/linux/swap.h |  3 ++-
>  mm/memcontrol.c      | 55 +++++++++++++++++++++++++++++++++++---------
>  mm/vmscan.c          | 13 +++++++++--

Documentation/admin-guide/cgroup-v2.rst is feeling unloved!

Please check whether this interface change can lead to
non-backward-compatible userspace.  If someone's script does the above
echo command, will it break on older kernels?  If so, does it matter?