netdev - Re: [PATCH net-next] selftests/net: calibrate txtimestamp

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Message-ID: <20240130145411.GK351311@kernel.org>
Date: Tue, 30 Jan 2024 15:54:11 +0100
From: Simon Horman <horms@...nel.org>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
	edumazet@...gle.com, pabeni@...hat.com,
	linux-kselftest@...r.kernel.org,
	Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] selftests/net: calibrate txtimestamp

On Fri, Jan 26, 2024 at 09:31:51PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
> 
> The test sends packets and compares enqueue, transmit and Ack
> timestamps with expected values. It installs netem delays to increase
> latency between these points.
> 
> The test proves flaky in virtual environment (vng). Increase the
> delays to reduce variance. Scale measurement tolerance accordingly.
> 
> Time sensitive tests are difficult to calibrate. Increasing delays 10x
> also increases runtime 10x, for one. And it may still prove flaky at
> some rate.
> 
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

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