Introduce support for configuring cpus and mems for processes using
cgroup v2 CPUSET controller. This allows users to limit which cpus
and memory NUMA nodes can be used by processes to better utilize
system resources.
The cgroup v2 interfaces to control it are cpuset.cpus and cpuset.mems
where the requested configuration is written. However, it doesn't mean
that the requested configuration will be actually used as parent cgroup
may limit the cpus or mems as well. In order to reflect the real
configuration cgroup v2 provides read-only files cpuset.cpus.effective
and cpuset.mems.effective which are exported to users as well.
The current code has multiple issues and it should never be done like
that. If someone updates list of allowed devices we should attach new
program before we remove the old one for two reasons:
1. It takes some time to attach new program so there is a period of time
when all devices are allowed.
2. BPF programs have limit for number of instructions (4096) and if user
adds a lot of devices we might hit the instruction limit and the new
program will not be accepted which will result in allow all devices
because the old program was already removed.
In order to attach the new program before we remove the old one we need
to use BPF_F_ALLOW_MULTI flag every time.
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
If enabling controller for some reason fails we need to clear error
for the FILE stream. Enabling remaining controllers would otherwise
fail because write_string_stream_ts() checks for ferror(f) and returns
-EIO if there is one.
Broken by commit <77fa610b22>.
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Pavel Hrdina