On Thu, 13 Aug 2020, Sumera Priyadarsini wrote:
> > > On Thu, 13 Aug, 2020, 1:45 AM Julia Lawall, <julia.law...@inria.fr> wrote: > > > 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. > > > How does this sound? > > However, when all available threads are used, a decrease in performance was > noted. The elapsed time was minimum when at most one thread per core was > used. This looks better, thanks. julia > > > > > > 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. > > > Alright, will add this. > > > thanks, > julia > > > > > Signed-off-by: Sumera Priyadarsini <sylphrena...@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 > > co...@systeme.lip6.fr > > https://systeme.lip6.fr/mailman/listinfo/cocci > > > > >
