Messages in this thread | | | Date | Wed, 12 Aug 2020 22:15:04 +0200 (CEST) | From | Julia Lawall <> | Subject | Re: [Cocci] [PATCH] scripts: coccicheck: Change default value for parallelism |
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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 >
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