[PATCH net-next] selftests: net: speed up pmtu.sh by avoiding unnecessary cleanup

[PATCH net-next] selftests: net: speed up pmtu.sh by avoiding unnecessary cleanup

[Jakub Kicinski]

The pmtu test takes nearly an hour when run on a debug kernel
(10min on a normal kernel, so the debug slow down is quite significant).
NIPA tries to ensure all results are delivered by a certain deadline
so this prevents it from retrying the test in case of a flake.

Looks like one of the slowest operations in the test is calling out
to ./openvswitch/ovs-dpctl.py to remove potential leftover OvS interfaces.
Check whether the interfaces exist in the first place in sysfs,
since it can be done directly in bash it is very fast.

This should save us around 20-30% of the test runtime.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/testing/selftests/net/pmtu.sh | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
index 88e914c4eef9..a3323c21f001 100755
--- a/tools/testing/selftests/net/pmtu.sh
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -1089,10 +1089,11 @@ cleanup() {
 
 	cleanup_all_ns
 
-	ip link del veth_A-C		2>/dev/null
-	ip link del veth_A-R1		2>/dev/null
-	cleanup_del_ovs_internal
-	cleanup_del_ovs_vswitchd
+	[ -e "/sys/class/net/veth_A-C"  ] && ip link del veth_A-C
+	[ -e "/sys/class/net/veth_A-R1" ] && ip link del veth_A-R1
+	[ -e "/sys/class/net/ovs_br0"   ] && cleanup_del_ovs_internal
+	[ -e "/sys/class/net/ovs_br0"   ] && cleanup_del_ovs_vswitchd
+
 	rm -f "$tmpoutfile"
 }
 
-- 
2.51.0

Re: [PATCH net-next] selftests: net: speed up pmtu.sh by avoiding unnecessary cleanup

[Simon Horman]

On Sat, Sep 06, 2025 at 02:45:35PM -0700, Jakub Kicinski wrote:
> The pmtu test takes nearly an hour when run on a debug kernel
> (10min on a normal kernel, so the debug slow down is quite significant).
> NIPA tries to ensure all results are delivered by a certain deadline
> so this prevents it from retrying the test in case of a flake.
> 
> Looks like one of the slowest operations in the test is calling out
> to ./openvswitch/ovs-dpctl.py to remove potential leftover OvS interfaces.
> Check whether the interfaces exist in the first place in sysfs,
> since it can be done directly in bash it is very fast.
> 
> This should save us around 20-30% of the test runtime.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

It would be interesting to know why this is so slow.
But I agree that avoiding unnecessary work is a good approach
if it is slow. And that appears to be the case.

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net-next] selftests: net: speed up pmtu.sh by avoiding unnecessary cleanup

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Sat,  6 Sep 2025 14:45:35 -0700 you wrote:
> The pmtu test takes nearly an hour when run on a debug kernel
> (10min on a normal kernel, so the debug slow down is quite significant).
> NIPA tries to ensure all results are delivered by a certain deadline
> so this prevents it from retrying the test in case of a flake.
> 
> Looks like one of the slowest operations in the test is calling out
> to ./openvswitch/ovs-dpctl.py to remove potential leftover OvS interfaces.
> Check whether the interfaces exist in the first place in sysfs,
> since it can be done directly in bash it is very fast.
> 
> [...]

Here is the summary with links:
  - [net-next] selftests: net: speed up pmtu.sh by avoiding unnecessary cleanup
    https://git.kernel.org/netdev/net-next/c/1c0353a6df82

You are awesome, thank you!
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