[RFC PATCH 0/2] sched/fair migration reduction features

[Mathieu Desnoyers]

Hi,

This series introduces two new scheduler features: UTIL_FITS_CAPACITY
and SELECT_BIAS_PREV. When used together, they achieve a 47% speedup of
a hackbench workload which leaves some idle CPU time on a 192-core AMD
EPYC.

The main metrics which are significantly improved are:

- cpu-migrations are reduced by 93%,
- CPU utilization is increased by 22%.

Feedback is welcome. I am especially interested to learn whether this
series has positive or detrimental effects on performance of other
workloads.

Thanks,

Mathieu

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Valentin Schneider <vschneid@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>
Cc: Swapnil Sapkal <Swapnil.Sapkal@xxxxxxx>
Cc: Aaron Lu <aaron.lu@xxxxxxxxx>
Cc: Chen Yu <yu.c.chen@xxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxx>
Cc: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Cc: Gautham R . Shenoy <gautham.shenoy@xxxxxxx>
Cc: x86@xxxxxxxxxx

Mathieu Desnoyers (2):
  sched/fair: Introduce UTIL_FITS_CAPACITY feature
  sched/fair: Introduce SELECT_BIAS_PREV to reduce migrations

 kernel/sched/fair.c     | 77 ++++++++++++++++++++++++++++++++++++-----
 kernel/sched/features.h | 12 +++++++
 kernel/sched/sched.h    |  5 +++
 3 files changed, 86 insertions(+), 8 deletions(-)

-- 
2.39.2