On 1/19/24 05:24, Paul E. McKenney wrote:
On Wed, Jan 17, 2024 at 11:35:03AM -0500, Waiman Long wrote:
This patch series is based on the RFC patch from Frederic [1]. Instead of offering RCU_NOCB as a separate option, it is now lumped into a root-only cpuset.cpus.isolation_full flag that will enable all the additional CPU isolation capabilities available for isolated partitions if set. RCU_NOCB is just the first one to this party. Additional dynamic CPU isolation capabilities will be added in the future.
The first 2 patches are adopted from Federic with minor twists to fix merge conflicts and compilation issue. The rests are for implementing the new cpuset.cpus.isolation_full interface which is essentially a flag to globally enable or disable full CPU isolation on isolated partitions. On read, it also shows the CPU isolation capabilities that are currently enabled. RCU_NOCB requires that the rcu_nocbs option be present in the kernel boot command line. Without that, the rcu_nocb functionality cannot be enabled even if the isolation_full flag is set. So we allow users to check the isolation_full file to verify that if the desired CPU isolation capability is enabled or not.
Only sanity checking has been done so far. More testing, especially on the RCU side, will be needed.
There has been some discussion of simplifying the (de-)offloading code to handle only offline CPUs. Along with some discussion of eliminating the (de-)offloading capability altogehter.
We clearly should converge on the capability to be provided before exposing this to userspace. ;-)
Would you mind giving me a pointer to the discussion of simplifying the de-offloading code to handle only offline CPUs?
Thanks, Longman