Hi, On Mon, Dec 19, 2022 at 06:52:50PM +0000, Colton Lewis wrote: > This loop logic is broken for machines with a number of CPUs that > isn't a power of two. A machine with 8 CPUs will test with MAX_SMP=8 > but a machine with 12 CPUs will test with MAX_SMP=6 because 12 >> 2 == > 6. This can, in rare circumstances, lead to different test results > depending only on the number of CPUs the machine has. I do think removing the loop is a good idea. I tested this patch, and when running a single test, it makes the run 3 seconds faster on an Cortex-A53 for me - selftest-smp and selftest-vectors-kernel went from taking 12s to 9s. Doesn't make much of a difference when running all the tests (those take for me 5m10s without the patch, 5m6.5s with the patch), but when running a single test the 25% speed improvement is noticeable. Though I'm not sure how you managed to get MAX_SMP to go down to 6 cores on a 12 core machine. MAX_SMP is initialized to $(getconf _NPROCESSORS_ONLN), so the body of the loop should never execute. I also tried it on a 6 core machine, and MAX_SMP was 6, not 3. Am I missing something? Thanks, Alex > > The loop is safe to remove with no side effects. It has an explanitory > comment explaining that it only applies to kernels <=v4.3 on arm and > suggestion deletion when it becomes tiresome to maintain. > > Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx> > --- > scripts/runtime.bash | 14 -------------- > 1 file changed, 14 deletions(-) > > diff --git a/scripts/runtime.bash b/scripts/runtime.bash > index f8794e9..18a8dd7 100644 > --- a/scripts/runtime.bash > +++ b/scripts/runtime.bash > @@ -183,17 +183,3 @@ function run() > > return $ret > } > - > -# > -# Probe for MAX_SMP, in case it's less than the number of host cpus. > -# > -# This probing currently only works for ARM, as x86 bails on another > -# error first. Also, this probing isn't necessary for any ARM hosts > -# running kernels later than v4.3, i.e. those including ef748917b52 > -# "arm/arm64: KVM: Remove 'config KVM_ARM_MAX_VCPUS'". So, at some > -# point when maintaining the while loop gets too tiresome, we can > -# just remove it... > -while $RUNTIME_arch_run _NO_FILE_4Uhere_ -smp $MAX_SMP \ > - |& grep -qi 'exceeds max CPUs'; do > - MAX_SMP=$((MAX_SMP >> 1)) > -done > -- > 2.39.0.314.g84b9a713c41-goog >
