On Thu, 24 Sep 2020, Sumera Priyadarsini wrote: > By default, coccicheck utilizes all available threads to implement > parallelisation. However, when all available threads are used, > a decrease in performance is noted. The elapsed time is minimum > when at most one thread per core is used. > > For example, on benchmarking the semantic patch kfree.cocci for > usb/serial using hyperfine, the outputs obtained for J=5 and J=2 > are 1.32 and 1.90 times faster than those for J=10 and J=9 > respectively for two separate runs. For the larger drivers/staging > directory, minimium elapsed time is obtained for J=3 which is 1.86 > times faster than that for J=12. The optimal J value does not > exceed 6 in any of the test runs. The benchmarks are run on a machine > with 6 cores, with 2 threads per core, i.e, 12 hyperthreads in all. > > To improve performance, modify coccicheck to use at most only > one thread per core by default. > > Signed-off-by: Sumera Priyadarsini <sylphrenadin@xxxxxxxxx> I have applied this one, so just the patch on the docuemtnation needs to be improved. julia > > --- > Changes in V2: > - Change commit message as suggested by Julia Lawall > Changes in V3: > - Use J/2 as optimal value for machines with more > than 8 hyperthreads as well. > --- > scripts/coccicheck | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/scripts/coccicheck b/scripts/coccicheck > index e04d328210ac..a72aa6c037ff 100755 > --- a/scripts/coccicheck > +++ b/scripts/coccicheck > @@ -75,8 +75,13 @@ 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 $NPROC -gt 2 ] ; then > + NPROC=$((NPROC/2)) > + fi > else > NPROC="$J" > fi > -- > 2.25.1 > > _______________________________________________ > Cocci mailing list > Cocci@xxxxxxxxxxxxxxx > https://systeme.lip6.fr/mailman/listinfo/cocci >
