kernel/configs: enable swap extension (CONFIG_MEMCG_SWAP)

[devimc]

libcontainer limits the memory+swap usage by writing the limit at
/sys/fs/cgroup/memory/docker/$CONTID/memory.memsw.limit_in_bytes, this path
doesn't exist if CONFIG_MEMCG_SWAP and CONFIG_MEMCG_SWAP_ENABLED are not
enabled.

fixes #103

Signed-off-by: Julio Montes [email protected]

[grahamwhaley]

It somehow feels sort of wrong, enabling SWAP in the kernel when we have no swap devices in the container.
For reference, on all of my 'default out of the box' Ubuntu machines I believe, when I run host side something link docker run --rm -ti -m 8G busybox sh I get the warning:

WARNING: Your kernel does not support swap limit capabilities or the cgroup is not mounted, Memory limited without swap.
Which is implying to me either that the missing swap option didn't matter, or it was somehow limited by a different method.
afaict, the code that issues that warning is at:
https://github.com/moby/moby/blob/5fc12449d830ae9005138fb3d3782728fa8d137a/daemon/daemon_unix.go#L368

Does that bear relevance here?

[devimc]

@grahamwhaley yes, I know it looks weird (enable swap when we don't have swap) but libcontainer specifies the maximum usage permitted for user memory plus swap space, I'll take a look to source code to see if it's possible to skip/disable it.

Take a look #103

[jodh-intel]

Any update on this @devimc? Also, why no updated to ppc64le's config?

/cc @nitkon.

[devimc]

@jodh-intel I'm waiting for review, ppc64le already has that config

[jodh-intel]

Ah - thiis'll be related to #8, #55, #56 then ;)

[devimc]

re-ping @kata-containers/packaging

[jodh-intel]

lgtm

/cc @nitkon.

[nitkon]

@jodh-intel : Its already enabled in ppc64le kernel config file and this patch changes only for x86 and arm.

[grahamwhaley]

I guess you did the research and didn't find a way to skip/disable it then @devimc ?

[devimc]

@grahamwhaley that's correct, we need these flags to honour memory constrains in the VM

[grahamwhaley]

OK, given @devimc 's confirmation,
lgtm

[bergwolf]

@devimc What about arm config? It doesn't enable swap yet.

cc @kalyxin02 @Weichen81

[bergwolf]

oops, my bad, arm config is added there.

/lgtm

[bergwolf]

Let's merge it!

[Weichen81]

Thanks @devimc ; )