Possible scriping bug in rcutorture/kvm.sh

Possible scriping bug in rcutorture/kvm.sh

[Joel Fernandes]

Hello,
Currently with my ARM machine of 288 CPUs, I am only seeing 56 of them used at a
time. Any ideas if this is a bug or I am doing something wrong?

I started a batch of 36 SRCU-P runs, which is exactly 1 batch:

$ sudo tools/testing/selftests/rcutorture/bin/kvm.sh --duration 120 --allcpus
--configs "10*SRCU-P" --dryrun batches
1 SRCU-P 8


1 SRCU-P.2 8

1 SRCU-P.3 8

1 SRCU-P.4 8

1 SRCU-P.5 8

1 SRCU-P.6 8

1 SRCU-P.7 8

1 SRCU-P.8 8

1 SRCU-P.9 8

1 SRCU-P.10 8

But, when I run it via:
$ sudo tools/testing/selftests/rcutorture/bin/kvm.sh --duration 240 --cpus 288
--configs "36*SRCU-P"

ps shows me only 7 qemu instances of 8 CPUs each. However, weirdly it is only 1
thread for each instance (thus its not even 56 CPUs, but rather 7 or so).

1496915 root      20   0 1684276 256996  66816 R  90.9   0.2   8:38.06
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+
1496913 root      20   0 1684276 256996  66816 R  89.7   0.2   8:50.53
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+
1496929 root      20   0 1684276 256996  66816 R  89.3   0.2   8:44.53
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+
1496938 root      20   0 1684276 256996  66816 R  82.8   0.2   8:46.03
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+
1496922 root      20   0 1684276 256996  66816 R  82.1   0.2   8:57.83
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+
1496908 root      20   0 1684276 256996  66816 R  81.5   0.2   8:50.59
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+
1496920 root      20   0 1684276 256996  66816 R  63.6   0.2   8:51.46
qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
-machine virt,gic-version=host -cpu host+

Thanks.

Re: Possible scriping bug in rcutorture/kvm.sh

[Paul E. McKenney]

On Thu, Apr 10, 2025 at 09:59:07AM -0400, Joel Fernandes wrote:
> Hello,
> Currently with my ARM machine of 288 CPUs, I am only seeing 56 of them used at a
> time. Any ideas if this is a bug or I am doing something wrong?

I regularly run with 80 CPUs, but perhaps the script's check for the
number of CPUs is broken on ARM?  It currently relies on this:

	getconf _NPROCESSORS_ONLN

(See identify_qemu_vcpus() in functions.sh.)

What should it be doing instead on ARM?

Huh.  56 does not go evenly into 288, either.  Search me!

							Thanx, Paul

> I started a batch of 36 SRCU-P runs, which is exactly 1 batch:
> 
> $ sudo tools/testing/selftests/rcutorture/bin/kvm.sh --duration 120 --allcpus
> --configs "10*SRCU-P" --dryrun batches
> 1 SRCU-P 8
> 
> 
> 1 SRCU-P.2 8
> 
> 1 SRCU-P.3 8
> 
> 1 SRCU-P.4 8
> 
> 1 SRCU-P.5 8
> 
> 1 SRCU-P.6 8
> 
> 1 SRCU-P.7 8
> 
> 1 SRCU-P.8 8
> 
> 1 SRCU-P.9 8
> 
> 1 SRCU-P.10 8
> 
> But, when I run it via:
> $ sudo tools/testing/selftests/rcutorture/bin/kvm.sh --duration 240 --cpus 288
> --configs "36*SRCU-P"
> 
> ps shows me only 7 qemu instances of 8 CPUs each. However, weirdly it is only 1
> thread for each instance (thus its not even 56 CPUs, but rather 7 or so).
> 
> 1496915 root      20   0 1684276 256996  66816 R  90.9   0.2   8:38.06
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 1496913 root      20   0 1684276 256996  66816 R  89.7   0.2   8:50.53
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 1496929 root      20   0 1684276 256996  66816 R  89.3   0.2   8:44.53
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 1496938 root      20   0 1684276 256996  66816 R  82.8   0.2   8:46.03
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 1496922 root      20   0 1684276 256996  66816 R  82.1   0.2   8:57.83
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 1496908 root      20   0 1684276 256996  66816 R  81.5   0.2   8:50.59
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 1496920 root      20   0 1684276 256996  66816 R  63.6   0.2   8:51.46
> qemu-system-aarch64 -enable-kvm -display none -no-reboot -smp 8 -net none
> -machine virt,gic-version=host -cpu host+
> 
> Thanks.
> 
> 

Re: Possible scriping bug in rcutorture/kvm.sh

[Joel Fernandes]

On 4/10/2025 10:31 AM, Paul E. McKenney wrote:
> On Thu, Apr 10, 2025 at 09:59:07AM -0400, Joel Fernandes wrote:
>> Hello,
>> Currently with my ARM machine of 288 CPUs, I am only seeing 56 of them used at a
>> time. Any ideas if this is a bug or I am doing something wrong?
> 
> I regularly run with 80 CPUs, but perhaps the script's check for the
> number of CPUs is broken on ARM?  It currently relies on this:
> 
> 	getconf _NPROCESSORS_ONLN
> 
> (See identify_qemu_vcpus() in functions.sh.)
> 
> What should it be doing instead on ARM?

I am guessing nothing different because it still gives 288:

$ getconf _NPROCESSORS_ONLN
288

> 
> Huh.  56 does not go evenly into 288, either.  Search me!
I think its failing because its only running the first SRCU-P for me and failing
for the rest in the batch because:

I see this for the rest of the runs: "Initial build failed, not running KVM":

I think its because this line is failing for ARM because it does not have a
bzImage (it instead has Image):

if test "$base_resdir" != "$resdir" && test -f $base_resdir/bzImage && test -f
$base_resdir/vmlinux

I'll try this and see if it works (sorry my thunderbird is wrapping the diff..):

diff --git a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
index ad79784e552d..957800c9ffba 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh
@@ -73,7 +73,7 @@ config_override_param "$config_dir/CFcommon.$(uname -m)" KcList \
 cp $T/KcList $resdir/ConfigFragment

 base_resdir=`echo $resdir | sed -e 's/\.[0-9]\+$//'`
-if test "$base_resdir" != "$resdir" && test -f $base_resdir/bzImage && test -f
$base_resdir/vmlinux
+if test "$base_resdir" != "$resdir" && (test -f $base_resdir/bzImage || test -f
$base_resdir/Image) && test -f $base_resdir/vmlinux
 then
        # Rerunning previous test, so use that test's kernel.
        QEMU="`identify_qemu $base_resdir/vmlinux`"

Thanks.