Re: [PATCH 2/2] torture: Make thread detection more robust by using lspcu

On Fri, Feb 25, 2022 at 06:49:32AM +0100, Paul Menzel wrote:

Dear Paul,

Am 24.02.22 um 21:56 schrieb Paul E. McKenney:

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On Thu, Feb 24, 2022 at 09:24:11AM +0100, Paul Menzel wrote:

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Am 22.02.22 um 18:43 schrieb Paul E. McKenney:

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On Tue, Feb 22, 2022 at 01:07:17PM +0100, Paul Menzel wrote:

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For consecutive numbers *lscpu* collapses the output and just shows the range with start and end. The processors are numbered that way on POWER8.

  $ sudo ppc64_cpu --smt=8
  $ lscpu | grep '^NUMA node'
  NUMA node(s):                    2
  NUMA node0 CPU(s):               0-79
  NUMA node8 CPU(s):               80-159

This causes the heuristic to detect the number threads per core, looking for the number after the first comma, to fail, and QEMU aborts because of invalid arguments.

  $ lscpu | sed -n -e '/^NUMA node0/s/^[^,]*,\([0-9]*\),.*$/\1/p'
  $

(Before the last patch, the whole line was returned.)

  $ lscpu | grep '^NUMA node0' | sed -e 's/^[^,-]*(,|\-)\([0-9]*\),.*$/\1/'
  NUMA node0 CPU(s):               0-79

*lscpu* shows the number of threads per core, so use that value directly.

  $ sudo ppc64_cpu --smt=8
  $ lscpu | grep 'Thread(s) per core'
  Thread(s) per core:              8
  $ sudo ppc64_cpu --smt=off
  $ lscpu | grep 'Thread(s) per core'
  Thread(s) per core:              1

Note, the replaced heuristic is also incorrect for that case, where the threads per core are disabled.

  $ lscpu | sed -n -e '/^NUMA node0/s/^[^,]*,\([0-9]*\),.*$/\1/p'
  8

Signed-off-by: Paul Menzel pmenzel@molgen.mpg.de

Makes sense, and thank you for chasing this down and for the fix!

But should this patch and 1/2 be merged? Or am I confused and they are somehow affecting two different lines of scripting?

You are right. I guess with 1/2 I just wanted to document clearly, what I learned in #sed@irc.libera.chat, that means, how to avoid using grep, when sed is used.

Nothing wrong with that!

I have merged the two patches as shown below. Does this work for you?

					Thanx, Paul

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commit 9f0daba62e958c31326c7a9eae33651e3a3cc6b4 Author: Paul Menzel pmenzel@molgen.mpg.de Date: Tue Feb 22 13:07:16 2022 +0100

 torture: Make thread detection more robust by using lspcu
 For consecutive numbers the lscpu command collapses the output and just
 shows the range with start and end. The processors are numbered that
 way on POWER8.
     $ sudo ppc64_cpu --smt=8
     $ lscpu | grep '^NUMA node'
     NUMA node(s):                    2
     NUMA node0 CPU(s):               0-79
     NUMA node8 CPU(s):               80-159
 This causes the heuristic to detect the number threads per core, looking
 for the number after the first comma, to fail, and QEMU aborts because of
 invalid arguments.
     $ lscpu | grep '^NUMA node0' | sed -e 's/^[^,-]*(,|\-)\([0-9]*\),.*$/\1/'
     NUMA node0 CPU(s):               0-79
 But the lscpu command shows the number of threads per core:
     $ sudo ppc64_cpu --smt=8
     $ lscpu | grep 'Thread(s) per core'
     Thread(s) per core:              8
     $ sudo ppc64_cpu --smt=off
     $ lscpu | grep 'Thread(s) per core'
     Thread(s) per core:              1
 This commit therefore directly uses that value.

Maybe extend: …, and replaces `grep` by using using sed’s switch `-n` and the command p.

Ah, good point -- I will update this on the next rebase.

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 Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
 Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/tools/testing/selftests/rcutorture/bin/functions.sh b/tools/testing/selftests/rcutorture/bin/functions.sh index c35ba24f994c3..66d0414d8e4bc 100644 --- a/tools/testing/selftests/rcutorture/bin/functions.sh +++ b/tools/testing/selftests/rcutorture/bin/functions.sh @@ -301,7 +301,7 @@ specify_qemu_cpus () { echo $2 -smp $3 ;; qemu-system-ppc64)

• 	nt="`lscpu | grep '^NUMA node0' | sed -e 's/^[^,]*,\([0-9]*\),.*$/\1/'`"
  

• 	nt="`lscpu | sed -n 's/^Thread(s) per core:\s*//p'`"
  echo $2 -smp cores=`expr \( $3 + $nt - 1 \) / $nt`,threads=$nt
  ;;
  

  esac

Thank you for doing that, and sorry for the extra work.

No complaints! You are after all testing on powerpc, and getting that working better is a good thing.

Thanx, Paul