Date: Mon, 30 Sep 2024 22:27:28 +0200
Author: Steffen Nurpmeso <steffen@sdaoden.eu>
From: Steffen Nurpmeso <steffen@sdaoden.eu>
To: Jerome Marc <marcjero@yahoo.com>
Cc: ~alpine/users@lists.alpinelinux.org
Subject: Re: freeze / connection delay after idling for a while ?
Message-ID: <20240930202728._Cgmke2m@steffen%sdaoden.eu>
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 the world can make no bugs.

Jerome Marc wrote in
 <CAD1Ag0wW0nw-BR1aqKkD66LLO_yndJAy__i6yg9TWvU_Z6QEDA@mail.gmail.com>:
 |I just installed Alpine 3.20.3 on a RPI 2 in diskless mode.(headless,
 |minimal installation)
 |
 |I noticed that if I let the device idling, I have a few seconds latency
 |when I try to connect the machine with SSH for example. Even when connected
 |I can have my SSH session frozen for a few seconds if I do nothing in the
 |terminal.
 |I notice the same when using a nodejs app (HTTP) therefore this is a
 |general thing (not just about SSH)
 |
 |I don't see anything weird in logs. Any idea ? Is that a power saving
 |feature ?

It *could* be that cpupower-openrc is indeed the
tools/power/cpupower of the linux kernel sources, it seems to be
widely available (architecture-wise, on Alpine).
If that is so, then running it should output stuff like

  #?0|kent:~# bin/cpupower.sh
  analyzing CPU 0:
    driver: intel_pstate
    CPUs which run at the same hardware frequency: 0
    CPUs which need to have their frequency coordinated by software: 0
    maximum transition latency:  Cannot determine or is not supported.
    hardware limits: 400 MHz - 3.40 GHz
    available cpufreq governors: performance powersave
    current policy: frequency should be within 400 MHz and 3.40 GHz.
                    The governor "powersave" may decide which speed to use
                    within this range.
    current CPU frequency: Unable to call hardware
    current CPU frequency: 800 MHz (asserted by call to kernel)
    boost state support:
      Supported: yes
      Active: yes

On the reserve laptop however the EFI(BIOS) "always" sets back
cpupower, and we start with "powersave" governor and low
frequency, and so the initial decrypting of the hard disk takes
seeeeconds.  I btw drive it via

  #!/bin/sh -
  #@ /root/bin/cpupower.sh
  # cpupower is in Linux src, tools/power/cpupower

  : ${HOSTNAME:=$(uname -n)}

  if [ -f /root/hosts/${HOSTNAME}/cpupower ]; then
          . /root/hosts/${HOSTNAME}/cpupower
  else
          logger -s -t /root/bin/cpupower.sh "MISS /root/hosts/${HOSTNAME}/cpupower"
          exit 1
  fi

  if command -v cpupower >/dev/null 2>&1; then :; else
          logger -s -t /root/bin/cpupower.sh 'no cpupower tool'
          exit 1
  fi

  if [ $# -gt 0 ]; then
          x=
          case $1 in
          lo) x=$lo;;
          med) x=$med;;
          hi) x=$hi;;
          default) x=$default;;
          75) x=$x75;;
          *) echo >&2 'Synopsis: cpupower [lo|med|hi|default[|75]]';;
          esac
          [ -n "$x" ] && cpupower frequency-set -u $x
  fi

  cpupower frequency-info

and that /root/hosts/$HOSTNAME/cpupower is (here)

  #@ /root/hosts/self/cpupower
  lo='400M -g powersave'
  med='1600M -g powersave'
  hi='3400M -g performance'
  default='3400M -g powersave'
  x75='2500M -g performance'

(i use "hi" only for kernel and port builds).
It makes "a hell of a difference".

Other than that i have seen similar things because (a) the
kernel's crng came up slowly (up to 30 minutes at times), but this
*should* be a thing of the past (dunno Alpine 3.20, i always use
[edge]), or because of WiFi chip powersafe stuff, i usually do
that though, i use "iw dev $dev set power_save on":

  # iw dev wlp1s0 get power_save
  Power save: on

Other than that i am out of ideas.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)