tree edbd56fb3069895e1d8306df53aaa3d742a9bec8
parent 1a7c611546e552193180941ecf6b191e659db979
parent 2f88c8e802c8b128a155976631f4eb2ce4f3c805
author Linus Torvalds <torvalds@linux-foundation.org> 1693266219 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1693266219 -0700
mergetag object 2f88c8e802c8b128a155976631f4eb2ce4f3c805
 type commit
 tag sched-core-2023-08-28
 tagger Ingo Molnar <mingo@kernel.org> 1693255605 +0200
 
 Scheduler changes for v6.6:
 
 - The biggest change is introduction of a new iteration of the
   SCHED_FAIR interactivity code: the EEVDF ("Earliest Eligible Virtual
   Deadline First") scheduler.
 
   EEVDF too is a virtual-time scheduler, with two parameters (weight
   and relative deadline), compared to CFS that had weight only.
   It completely reworks the base scheduler: placement, preemption,
   picking -- everything.
 
   LWN.net, as usual, has a terrific writeup about EEVDF:
 
      https://lwn.net/Articles/925371/
 
   Preemption (both tick and wakeup) is driven by testing against
   a fresh pick. Because the tree is now effectively an interval
   tree, and the selection is no longer the 'leftmost' task,
   over-scheduling is less of a problem. A lot of the CFS
   heuristics are removed or replaced by more natural latency-space
   parameters & constructs.
 
   In terms of expected performance regressions: we'll and can fix
   everything where a 'good' workload misbehaves with the new scheduler,
   but EEVDF inevitably changes workload scheduling in a binary fashion,
   hopefully for the better in the overwhelming majority of cases,
   but in some cases it won't, especially in adversarial loads that
   got lucky with the previous code, such as some variants of hackbench.
   We are trying hard to err on the side of fixing all performance
   regressions, but we expect some inevitable post-release iterations
   of that process.
 
 - Improve load-balancing on hybrid x86 systems: enable cluster
   scheduling (again).
 
 - Improve & fix bandwidth-scheduling on nohz systems.
 
 - Improve bandwidth-throttling.
 
 - Use lock guards to simplify and de-goto-ify control flow.
 
 - Misc improvements, cleanups and fixes.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
 -----BEGIN PGP SIGNATURE-----
 
 iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmTtDOgRHG1pbmdvQGtl
 cm5lbC5vcmcACgkQEnMQ0APhK1iS4g//b9yewVW9OPxetKoN8zIJA0TjFYuuOVHK
 BlCJi5dbzXeCTrtENI65BRA7kPbTQ3AjwLRQ2BallAZ4dJceK0RhlZJvcrMNsm4e
 Adcpoch/FbqPKCrtAJQY04Ln1B244n/KyVifYett9220dMgTFQGJJYxrTc2G2+Kp
 F44vdUHzRczIE+KeOgBild1CwfKv5Zn5xgaXgtuoPLZtWBE0C1fSSzbK/PTINcUx
 bS4NVxK0CpOqSiNjnugV8KsYb71/0U6IgShBVjfHsrlBYigOH2NbVTH5xyjF8f83
 WxiGstlhxj+N6Kv4L6FOJIAr2BIggH82j3FaPACmv4c8pzEoBBbvlAJkfinLEgbn
 Povg3OF2t6uZ8NoHjeu3WxOjBsphbpkFz7H5nno1ibXSIR/JyUH5MdBPSx93QITB
 QoUKQpr/L8zWauWDOEzSaJjEsZbl8rkcIVq5Bk0bR3qn2xkZsIeVte+vCEu3+tBc
 b4JOZjq7AuPDqPnsBLvuyiFZ7zwsAfm+pOD5UF3/zbLjPn1N/7wTNQZ29zjc04jl
 SifpCZGgF1KlG8m8wNTlSfVvq0ksppCzJt+C6VFuejZ191IGpirQHn4Vp0sluMhC
 WRzXhb7v37Bq5JY10GMfeKb/jAiRs68kozhzqVPsBSAPS6I6jJssONgedq+LbQdC
 tFsmE9n09do=
 =XtCD
 -----END PGP SIGNATURE-----

Merge tag 'sched-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - The biggest change is introduction of a new iteration of the
   SCHED_FAIR interactivity code: the EEVDF ("Earliest Eligible Virtual
   Deadline First") scheduler

   EEVDF too is a virtual-time scheduler, with two parameters (weight
   and relative deadline), compared to CFS that had weight only. It
   completely reworks the base scheduler: placement, preemption, picking
   -- everything

   LWN.net, as usual, has a terrific writeup about EEVDF:

      https://lwn.net/Articles/925371/

   Preemption (both tick and wakeup) is driven by testing against a
   fresh pick. Because the tree is now effectively an interval tree, and
   the selection is no longer the 'leftmost' task, over-scheduling is
   less of a problem. A lot of the CFS heuristics are removed or
   replaced by more natural latency-space parameters & constructs

   In terms of expected performance regressions: we will and can fix
   everything where a 'good' workload misbehaves with the new scheduler,
   but EEVDF inevitably changes workload scheduling in a binary fashion,
   hopefully for the better in the overwhelming majority of cases, but
   in some cases it won't, especially in adversarial loads that got
   lucky with the previous code, such as some variants of hackbench. We
   are trying hard to err on the side of fixing all performance
   regressions, but we expect some inevitable post-release iterations of
   that process

 - Improve load-balancing on hybrid x86 systems: enable cluster
   scheduling (again)

 - Improve & fix bandwidth-scheduling on nohz systems

 - Improve bandwidth-throttling

 - Use lock guards to simplify and de-goto-ify control flow

 - Misc improvements, cleanups and fixes

* tag 'sched-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (43 commits)
  sched/eevdf/doc: Modify the documented knob to base_slice_ns as well
  sched/eevdf: Curb wakeup-preemption
  sched: Simplify sched_core_cpu_{starting,deactivate}()
  sched: Simplify try_steal_cookie()
  sched: Simplify sched_tick_remote()
  sched: Simplify sched_exec()
  sched: Simplify ttwu()
  sched: Simplify wake_up_if_idle()
  sched: Simplify: migrate_swap_stop()
  sched: Simplify sysctl_sched_uclamp_handler()
  sched: Simplify get_nohz_timer_target()
  sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset
  sched/rt: Fix sysctl_sched_rr_timeslice intial value
  sched/fair: Block nohz tick_stop when cfs bandwidth in use
  sched, cgroup: Restore meaning to hierarchical_quota
  MAINTAINERS: Add Peter explicitly to the psi section
  sched/psi: Select KERNFS as needed
  sched/topology: Align group flags when removing degenerate domain
  sched/fair: remove util_est boosting
  sched/fair: Propagate enqueue flags into place_entity()
  ...