Re: [Cocci] [PATCH] scripts: coccicheck: Change default value for parallelism
On Thu, 13 Aug 2020, Sumera Priyadarsini wrote: > > > On Thu, 13 Aug, 2020, 1:45 AM Julia Lawall, 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 > > --- > > 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 > > > > >___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [Cocci] [PATCH] scripts: coccicheck: Change default value for parallelism
On Thu, 13 Aug, 2020, 1:45 AM Julia Lawall, 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. > > 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 > > --- > > 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 > > > ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
Re: [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 > --- > 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 > ___ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
[Cocci] [PATCH] scripts: coccicheck: Change default value for parallelism
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. Hence, to improve performance, modify coccicheck to use only one thread per core atmost. 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. Signed-off-by: Sumera Priyadarsini --- 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
