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Date:   Fri, 15 Sep 2023 14:43:54 +0200
From:   peterz@infradead.org
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Subject: [PATCH 0/2] sched/eevdf: sched_attr::sched_runtime slice hint
Precedence: bulk

Hi,

As promised a while ago, here is a new version of the variable slice length
hint stuff.  Back when I asked for comments on the latency-nice vs slice length
thing, there was very limited feedback on-list, a number of people have
expressed interrest in the slice length hint.


I'm still working on improving the wakeup latency -- but esp. after commit:

  63304558ba5d ("sched/eevdf: Curb wakeup-preemption")

it needs a little more work. Everything I tried so far made it worse.

As is it behaves ok-ish:

  root@ivb-ep:~/bench# cat doit-latency-slice.sh
  #!/bin/bash

  perf bench sched messaging -g 40 -l 12000 &

  sleep 1
  chrt3 -o --sched-runtime $((`cat /debug/sched/base_slice_ns`*10)) 0 cyclictest --policy other -D 5 -q   -H 20000 --histfile data.txt ; grep Latencies data.txt
  chrt3 -o --sched-runtime 0 0 cyclictest --policy other -D 5 -q   -H 20000 --histfile data.txt ; grep Latencies data.txt
  chrt3 -o --sched-runtime $((`cat /debug/sched/base_slice_ns`/10)) 0 cyclictest --policy other -D 5 -q   -H 20000 --histfile data.txt ; grep Latencies data.txt

  wait $!
  root@ivb-ep:~/bench# ./doit-latency-slice.sh
  # Running 'sched/messaging' benchmark:
  # /dev/cpu_dma_latency set to 0us
  # Min Latencies: 00060
  # Avg Latencies: 00990
  # Max Latencies: 224925
  # /dev/cpu_dma_latency set to 0us
  # Min Latencies: 00020
  # Avg Latencies: 00656
  # Max Latencies: 37595
  # /dev/cpu_dma_latency set to 0us
  # Min Latencies: 00016
  # Avg Latencies: 00354
  # Max Latencies: 16687
  # 20 sender and receiver processes per group
  # 40 groups == 1600 processes run

       Total time: 38.246 [sec]


(chrt3 is a hacked up version of util-linux/chrt that allows --sched-runtime unconditionally)