sched-core-2021-06-28

 - Changes to core scheduling facilities:

    - Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
      coordinated scheduling across SMT siblings. This is a much
      requested feature for cloud computing platforms, to allow
      the flexible utilization of SMT siblings, without exposing
      untrusted domains to information leaks & side channels, plus
      to ensure more deterministic computing performance on SMT
      systems used by heterogenous workloads.

      There's new prctls to set core scheduling groups, which
      allows more flexible management of workloads that can share
      siblings.

    - Fix task->state access anti-patterns that may result in missed
      wakeups and rename it to ->__state in the process to catch new
      abuses.

 - Load-balancing changes:

     - Tweak newidle_balance for fair-sched, to improve
       'memcache'-like workloads.

     - "Age" (decay) average idle time, to better track & improve workloads
       such as 'tbench'.

     - Fix & improve energy-aware (EAS) balancing logic & metrics.

     - Fix & improve the uclamp metrics.

     - Fix task migration (taskset) corner case on !CONFIG_CPUSET.

     - Fix RT and deadline utilization tracking across policy changes

     - Introduce a "burstable" CFS controller via cgroups, which allows
       bursty CPU-bound workloads to borrow a bit against their future
       quota to improve overall latencies & batching. Can be tweaked
       via /sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.

     - Rework assymetric topology/capacity detection & handling.

 - Scheduler statistics & tooling:

     - Disable delayacct by default, but add a sysctl to enable
       it at runtime if tooling needs it. Use static keys and
       other optimizations to make it more palatable.

     - Use sched_clock() in delayacct, instead of ktime_get_ns().

 - Misc cleanups and fixes.

Signed-off-by: Ingo Molnar <mingo@kernel.org>