Re: [RFC] memcg: Add swappiness to cgroup2

Chris Down
2019-12-25T14:05:52Z

Hi Hui,

Hui Zhu writes:
>Even if cgroup2 has swap.max, swappiness is still a very useful config.
>This commit add swappiness to cgroup2.

When submitting patches like this, it's important to explain *why* you want it
and what evidence there is. For example, how should one use this to compose a
reasonable system? Why aren't existing protection controls sufficient for your
use case? Where's the data?

Also, why would swappiness be something cgroup-specific instead of
hardware-specific, when desired swappiness is really largely about the hardware
you have in your system?

I struggle to think of situations where per-cgroup swappiness would be useful,
since it's really not a workload-specific setting.

Thanks,

Chris

>Signed-off-by: Hui Zhu <teawaterz@linux.alibaba.com>
>---
> mm/memcontrol.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>index c5b5f74..e966396 100644
>--- a/mm/memcontrol.c
>+++ b/mm/memcontrol.c
>@@ -7143,6 +7143,11 @@ static struct cftype swap_files[] = {
> .file_offset = offsetof(struct mem_cgroup, swap_events_file),
> .seq_show = swap_events_show,
> },
>+ {
>+ .name = "swappiness",
>+ .read_u64 = mem_cgroup_swappiness_read,
>+ .write_u64 = mem_cgroup_swappiness_write,
>+ },
> { } /* terminate */
> };
>
>--
>2.7.4
>
>