[Bug 1846844] [NEW] Procps: top -b does not display the correct CPU percentages

Simon Tideswell 1846844 at bugs.launchpad.net
Fri Oct 4 23:08:29 UTC 2019 

Public bug reported:

Affects: 2:3.3.12-3ubuntu1.2 (bionic) & 2:3.3.10-4ubuntu2.4 (xenial)

If I run 'top -b -n 1' the CPU percentages are the same every single
time. If I run with more iterations the CPU percentages of subsequent
iterations update in real time. If I run top interactively then the CPU
percentages correctly update in real time. Here's an example.

1) With n=1 the same CPU percentages are always displayed.

while true ; do top -b -n 1 | grep -E "^%Cpu" ; sleep 10; done
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st

2) With n=2 the second iteration shows a changing CPU percentage, but
the first is still clearly wrong.

while true ; do top -b -n 2 | grep -E "^%Cpu" ; sleep 10; done
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 27.3 us,  1.7 sy,  0.0 ni, 70.5 id,  0.0 wa,  0.0 hi,  0.4 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 50.9 us,  5.4 sy,  0.0 ni, 42.2 id,  0.1 wa,  0.0 hi,  1.4 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 63.3 us,  5.2 sy,  0.0 ni, 29.2 id,  0.1 wa,  0.0 hi,  2.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 43.3 us,  2.9 sy,  0.0 ni, 52.4 id,  0.1 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 38.0 us,  3.7 sy,  0.0 ni, 56.8 id,  0.2 wa,  0.0 hi,  1.4 si,  0.0 st
%Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
%Cpu(s): 47.9 us,  3.5 sy,  0.0 ni, 47.2 id,  0.1 wa,  0.0 hi,  1.2 si,  0.0 st

This affects both Xenial and Bionic.

** Affects: procps (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: batch procps top

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to procps in Ubuntu.
https://bugs.launchpad.net/bugs/1846844

Title:
  Procps: top -b does not display the correct CPU percentages

Status in procps package in Ubuntu:
  New

Bug description:
  Affects: 2:3.3.12-3ubuntu1.2 (bionic) & 2:3.3.10-4ubuntu2.4 (xenial)

  If I run 'top -b -n 1' the CPU percentages are the same every single
  time. If I run with more iterations the CPU percentages of subsequent
  iterations update in real time. If I run top interactively then the
  CPU percentages correctly update in real time. Here's an example.

  1) With n=1 the same CPU percentages are always displayed.

  while true ; do top -b -n 1 | grep -E "^%Cpu" ; sleep 10; done
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st

  2) With n=2 the second iteration shows a changing CPU percentage, but
  the first is still clearly wrong.

  while true ; do top -b -n 2 | grep -E "^%Cpu" ; sleep 10; done
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 27.3 us,  1.7 sy,  0.0 ni, 70.5 id,  0.0 wa,  0.0 hi,  0.4 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 50.9 us,  5.4 sy,  0.0 ni, 42.2 id,  0.1 wa,  0.0 hi,  1.4 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 63.3 us,  5.2 sy,  0.0 ni, 29.2 id,  0.1 wa,  0.0 hi,  2.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 43.3 us,  2.9 sy,  0.0 ni, 52.4 id,  0.1 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 38.0 us,  3.7 sy,  0.0 ni, 56.8 id,  0.2 wa,  0.0 hi,  1.4 si,  0.0 st
  %Cpu(s): 46.1 us,  4.1 sy,  0.2 ni, 48.1 id,  0.2 wa,  0.0 hi,  1.2 si,  0.0 st
  %Cpu(s): 47.9 us,  3.5 sy,  0.0 ni, 47.2 id,  0.1 wa,  0.0 hi,  1.2 si,  0.0 st

  This affects both Xenial and Bionic.

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1846844/+subscriptions

More information about the foundations-bugs mailing list