linux-kernel - Re: [PATCH v2 3/3] selftests/net: deflake GRO tests

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Message-ID: <67c08f55b0ae7_37f929294b0@willemb.c.googlers.com.notmuch>
Date: Thu, 27 Feb 2025 11:14:13 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Kevin Krakauer <krakauer@...gle.com>, 
 netdev@...r.kernel.org, 
 linux-kselftest@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, 
 Shuah Khan <shuah@...nel.org>, 
 linux-kernel@...r.kernel.org, 
 Kevin Krakauer <krakauer@...gle.com>
Subject: Re: [PATCH v2 3/3] selftests/net: deflake GRO tests

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. Reduce the flakiness by:
> 
> - Bumping retries to 6.
> - Setting napi_defer_hard_irqs to 1 to reduce the chance that GRO is
>   flushed prematurely. This also lets us reduce the gro_flush_timeout
>   from 1ms to 100us.
> 
> Tested: Ran `gro.sh -t large` 1000 times. There were no failures with
> this change. Ran inside strace to increase flakiness.
> 
> Signed-off-by: Kevin Krakauer <krakauer@...gle.com>

Nice! Thanks

Reviewed-by: Willem de Bruijn <willemb@...gle.com>

> ---
>  tools/testing/selftests/net/gro.sh        | 4 ++--
>  tools/testing/selftests/net/setup_veth.sh | 3 ++-
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/gro.sh b/tools/testing/selftests/net/gro.sh
> index aabd6e5480b8..9e3f186bc2a1 100755
> --- a/tools/testing/selftests/net/gro.sh
> +++ b/tools/testing/selftests/net/gro.sh
> @@ -18,10 +18,10 @@ run_test() {
>    "--smac" "${CLIENT_MAC}" "--test" "${test}" "--verbose" )
>  
>    setup_ns
> -  # Each test is run 3 times to deflake, because given the receive timing,
> +  # Each test is run 6 times to deflake, because given the receive timing,

Only if respinning: this was always imprecise: it is run up to X times. But
exits immediately on success.