Support docker cgroup limits

[tmds]

• The parsing would find the wrong '-' in lines like this:
  354 347 0:28 /system.slice/docker-654dd7b6b8bbfe1739ae3309b471e95ccc82b3a3f56b7879f0a811d68b5c4e1d.scope /sys/fs/cgroup/cpuacct,cpu ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,cpuacct,cpu
• In a docker container, the mount root and relative path in the cgroup have the same value, the relative path must not be appended to the mount point.

[tmds]

I've tested this as follows:
main.cpp

#include "/home/tmds/repos/coreclr/src/gc/unix/cgroup.cpp"

int main()
{
	CGroup cgroup;
	unsigned int cpus = 0;
	size_t mem = 0;
	if (cgroup.GetPhysicalMemoryLimit(&mem))
	{
		printf("mem: %zu\n", mem);
	}
	if (cgroup.GetCpuLimit(&cpus))
	{
		printf("cpu: %d\n", cpus);
	}
	return 0;
}

g++ main.cpp

Dockerfile

FROM fedora:25
RUN yum install -y libstdc++.so.6
WORKDIR /root
ADD ./a.out .
CMD ./a.out

$ docker build -t docker_limit .
$ docker run docker_limit
mem: 9223372036854771712
$ docker run --memory 300m docker_limit
mem: 314572800
$ docker run --cpu-period 1000 --cpu-quota 1000  docker_limit
mem: 9223372036854771712
cpu: 1
$ docker run --cpu-period 1000 --cpu-quota 2000  docker_limit
mem: 9223372036854771712
cpu: 2

[janvorli]

LGTM, thank you very much for finding and fixing it!

[janvorli]

@dotnet-bot test Tizen armel Cross Debug Build please

[tmds]

Thanks @janvorli

[tmds]

@janvorli I'm having a look at what commits could be picked to bring this to 2.0.x.
These can be cherry-picked without merge-conflicts and add support for docker mem&cpu limits:
16baed5, 0d53e14, 5596717
Does that seem like a proper set?
Can I do a PR for these to be included in a 2.0 branch? which branch?

[janvorli]

@tmds the release/2.0.0 branch is now frozen for the 2.0.1 release, we can back port it after it opens again.

[janvorli]

@tmds I've ported these three commits to release/2.0.0 branch, so it will be part of the 2.0.2 release.

[tmds]

Thanks @janvorli !