Re: [PATCH] selftests/net: deflake GRO tests and fix return value and output
flat view
From: Jakub Kicinski <kuba@kernel.org>
Date: 2025-02-21 01:04:10
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linux-kselftest, lkml
On Tue, 18 Feb 2025 08:45:55 -0800 Kevin Krakauer wrote:
GRO tests are timing dependent and can easily flake. This is partially mitigated in gro.sh by giving each subtest 3 chances to pass. However, this still flakes on some machines.
To be clear - are you running this over veth or a real device?
Set the device's napi_defer_hard_irqs to 50 so that GRO is less likely to immediately flush. This already happened in setup_loopback.sh, but wasn't added to setup_veth.sh. This accounts for most of the reduction in flakiness.
That doesn't make intuitive sense to me. If we already defer flushes why do we need to also defer IRQs?
quoted hunk ↗ jump to hunk
We also increase the number of chances for success from 3 to 6. `gro.sh -t <test>` now returns a passing/failing exit code as expected. gro.c:main no longer erroneously claims a test passes when running as a server. Tested: Ran `gro.sh -t large` 100 times with and without this change. Passed 100/100 with and 64/100 without. Ran inside strace to increase flakiness. Signed-off-by: Kevin Krakauer <redacted> --- tools/testing/selftests/net/gro.c | 8 +++++--- tools/testing/selftests/net/gro.sh | 5 +++-- tools/testing/selftests/net/setup_veth.sh | 1 + 3 files changed, 9 insertions(+), 5 deletions(-)diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c index b2184847e388..d5824eadea10 100644 --- a/tools/testing/selftests/net/gro.c +++ b/tools/testing/selftests/net/gro.c@@ -1318,11 +1318,13 @@ int main(int argc, char **argv) read_MAC(src_mac, smac); read_MAC(dst_mac, dmac); - if (tx_socket) + if (tx_socket) { gro_sender(); - else + } else { + /* Only the receiver exit status determines test success. */ gro_receiver(); + fprintf(stderr, "Gro::%s test passed.\n", testname); + } - fprintf(stderr, "Gro::%s test passed.\n", testname);
That seems quite separate to the stability fix?
quoted hunk ↗ jump to hunk
return 0; }diff --git a/tools/testing/selftests/net/gro.sh b/tools/testing/selftests/net/gro.sh index 02c21ff4ca81..703173f8c8a9 100755 --- a/tools/testing/selftests/net/gro.sh +++ b/tools/testing/selftests/net/gro.sh@@ -21,7 +21,7 @@ run_test() { # Each test is run 3 times to deflake, because given the receive timing, # not all packets that should coalesce will be considered in the same flow # on every try. - for tries in {1..3}; do + for tries in {1..6}; do # Actual test starts here ip netns exec $server_ns ./gro "${ARGS[@]}" "--rx" "--iface" "server" \ 1>>log.txt &@@ -100,5 +100,6 @@ trap cleanup EXIT if [[ "${test}" == "all" ]]; then run_all_tests else - run_test "${proto}" "${test}" + exit_code=$(run_test "${proto}" "${test}") + exit $exit_code
Also separate from stability? Let's split the patch up into logically separate changes.
quoted hunk ↗ jump to hunk
fi;diff --git a/tools/testing/selftests/net/setup_veth.sh b/tools/testing/selftests/net/setup_veth.sh index 1f78a87f6f37..9882ad730c24 100644 --- a/tools/testing/selftests/net/setup_veth.sh +++ b/tools/testing/selftests/net/setup_veth.sh@@ -12,6 +12,7 @@ setup_veth_ns() { [[ -e /var/run/netns/"${ns_name}" ]] || ip netns add "${ns_name}" echo 1000000 > "/sys/class/net/${ns_dev}/gro_flush_timeout" + echo 50 > "/sys/class/net/${ns_dev}/napi_defer_hard_irqs" ip link set dev "${ns_dev}" netns "${ns_name}" mtu 65535 ip -netns "${ns_name}" link set dev "${ns_dev}" up
-- pw-bot: cr