lkml.org 
[lkml]   [2020]   [Aug]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Cocci] [PATCH] scripts: coccicheck: Change default value for parallelism


On Wed, 12 Aug 2020, Sumera Priyadarsini wrote:

> By default, coccicheck utilizes all available threads to implement
> parallelisation. However, when hyperthreading is enabled, this leads
> to all threads per core being occupied resulting in longer wall-clock
> times and higher power consumption.

I have the feeling that the above sentence is not quite optimal.
Actually, using all of the available hardware threads would not be a bad
thing, if it was giving a benefit. The point is that it doesn't. It
makes the performance worse instead.

> Hence, to improve performance,
> modify coccicheck to use only one thread per core atmost.

"atmost" is not a word. It would be clearer to say "to use at most one
thread per core".

> In the cases where the total number of threads is more than 8 and
> hyperthreading is enabled, it was observed that optimum performance
> is achieved around one-fourth of the total number of cores.
> Modify the script further to accommodate this use case.

It would be nice to give some performance numbers and some information
about the machine used.

thanks,
julia

>
> Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
> ---
> scripts/coccicheck | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/scripts/coccicheck b/scripts/coccicheck
> index e04d328210ac..dd228dcc915e 100755
> --- a/scripts/coccicheck
> +++ b/scripts/coccicheck
> @@ -75,8 +75,17 @@ else
> OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
> fi
>
> + # Use only one thread per core by default if hyperthreading is enabled
> + THREADS_PER_CORE=$(lscpu | grep "Thread(s) per core: " | tr -cd [:digit:])
> if [ -z "$J" ]; then
> NPROC=$(getconf _NPROCESSORS_ONLN)
> + if [ $THREADS_PER_CORE -gt 1 -a $NPROC -gt 2 ] ; then
> + if [ $NPROC -gt 8 ] ; then
> + NPROC=$((NPROC/4))
> + else
> + NPROC=$((NPROC/2))
> + fi
> + fi
> else
> NPROC="$J"
> fi
> --
> 2.17.1
>
> _______________________________________________
> Cocci mailing list
> Cocci@systeme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
>

\
 
 \ /
  Last update: 2020-08-12 22:16    [W:0.047 / U:6.916 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site