build: add shm-size support

[crazy-max]

Follow-up moby/buildkit#2384
Fixes #418

vendor: moby/buildkit@ba673bb...8778943

# Dockerfile
FROM busybox
RUN df -kh /dev/shm

$ docker buildx build --no-cache --shm-size 128m .
#6 [2/2] RUN df -kh /dev/shm
#6 0.170 Filesystem                Size      Used Available Use% Mounted on
#6 0.170 shm                     128.0M         0    128.0M   0% /dev/shm
#6 DONE 0.2s

Signed-off-by: CrazyMax crazy-max@users.noreply.github.com

[tonistiigi]

I'm not sure about adding this to bake atm. I think we need to think through what to do with this and similar fields like ulimit, memory limits etc and if they should be grouped together under one field in bake. Network=host isn't currently in bake either.

[tonistiigi]

I'm not sure about adding this to bake atm. I think we need to think through what to do with this and similar fields like ulimit, memory limits etc and if they should be grouped together under one field in bake. Network=host isn't currently in bake either

Also, in a lot of cases, these fields make more sense in a dockerfile, per command.

[crazy-max]

I'm not sure about adding this to bake atm. I think we need to think through what to do with this and similar fields like ulimit, memory limits etc and if they should be grouped together under one field in bake. Network=host isn't currently in bake either.

Yes we can do that in a follow-up for bake sure. Maybe a resources field object in the HCL definition would be ok in this case.

Also, in a lot of cases, these fields make more sense in a dockerfile, per command.

While working on the gateway impl for shm-size, I had started to add RUN --shm=size=128m but it might require some changes related to what you said about resources.

[thaJeztah]

Also, in a lot of cases, these fields make more sense in a dockerfile, per command.

Yes, was slightly wondering this as well. Perhaps we should look when/why it was added in the classic builder, and what the exact use-case was.

While working on the gateway impl for shm-size, I had started to add RUN --shm=size=128m but it might require some changes related to what you said about resources.

In the end, shm is effectively just a tmpfs. Wondering if adding a size option to --mount would be an alternative (--mount=type=tmpfs.target=/dev/shm,size=xxx)
I recall there were similar discussions about docker service not having a --shm-size option.

[tonistiigi]

@thaJeztah That's a good point

@crazy-max I wonder if we should revert the llb part in moby/buildkit#2384 and instead add size. They are different in containerd but makes little sense to actually keep them separate here. In runtime specs it is handled as a regular mount as well.

[crazy-max]

I wonder if we should revert the llb part in moby/buildkit#2384 and instead add size.

@tonistiigi Yeah would make sense to change that in llb but keep the frontend attr specific to shm-size for the whole build right?

[tonistiigi]

but keep the frontend attr specific to shm-size for the whole build right?

yes

[crazy-max]

@tonistiigi Bake impl has been removed.

[thaJeztah]

(relates to moby/moby#40379)