cpusets, isolcpus: exclude isolcpus from load balancing in cpusets

Ensure that cpus specified with the isolcpus= boot commandline
option stay outside of the load balancing in the kernel scheduler.

Operations like load balancing can introduce unwanted latencies,
which is exactly what the isolcpus= commandline is there to prevent.

Previously, simply creating a new cpuset, without even touching the
cpuset.cpus field inside the new cpuset, would undo the effects of
isolcpus=, by creating a scheduler domain spanning the whole system,
and setting up load balancing inside that domain. The cpuset root
cpuset.cpus file is read-only, so there was not even a way to undo
that effect.

This does not impact the majority of cpusets users, since isolcpus=
is a fairly specialized feature used for realtime purposes.

Cc: Peter Zijlstra <[email protected]>
Cc: Clark Williams <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Luiz Capitulino <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: [email protected]
Signed-off-by: Rik van Riel <[email protected]>
Tested-by: David Rientjes <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: David Rientjes <[email protected]>
Acked-by: Zefan Li <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

0 files changed, 0 insertions, 0 deletions