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Subject[PATCH 0/7 v4] move update blocked load outside newidle_balance
Date
Joel reported long preempt and irq off sequence in newidle_balance because
of a large number of CPU cgroups in use and having to be updated. This
patchset moves the update outside newidle_imblance. This enables to early
abort during the updates in case of pending irq as an example.

Instead of kicking a normal ILB that will wakes up CPU which is already
idle, patch 6 triggers the update of statistics in the idle thread of
the CPU before selecting and entering an idle state.

Changes on v4:
- Add a dedicated bit for updating blocked load when entering idle.
This simplifies the management of concurrency with kick_ilb.

Changes on v3:
- Fixed a compilation error for !CONFIG_SMP && CONFIG_NO_HZ_COMMON
reported by kernel test robot <lkp@intel.com>
- Took advantage of this new version to add a short desciption for
nohz_run_idle_balance

Changes on v2:
- Fixed some typos and updated some comments
- Added more cleanup
- Changed to way to trigger ILB in idle thread context to remove a possible
race condition between the normal softirq ILB and this new mecanism. The
cpu can already be set in idle_cpus_mask because even if the cpu is added
later when entering idle, it might not have been removed yet from previous
idle phase.

Vincent Guittot (7):
sched/fair: remove update of blocked load from newidle_balance
sched/fair: remove unused return of _nohz_idle_balance
sched/fair: remove unused parameter of update_nohz_stats
sched/fair: merge for each idle cpu loop of ILB
sched/fair: reorder newidle_balance pulled_task tests
sched/fair: trigger the update of blocked load on newly idle cpu
sched/fair: reduce the window for duplicated update

kernel/sched/core.c | 2 +-
kernel/sched/fair.c | 118 +++++++++++++++++--------------------------
kernel/sched/idle.c | 6 +++
kernel/sched/sched.h | 7 +++
4 files changed, 60 insertions(+), 73 deletions(-)

--
2.17.1

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