netdev - Re: [PATCH net-next 6/9] selftests: drv-net: gro: use SO

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Message-ID: <878qd5292w.fsf@nvidia.com>
Date: Fri, 6 Feb 2026 16:19:26 +0100
From: Petr Machata <petrm@...dia.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: <davem@...emloft.net>, <netdev@...r.kernel.org>, <edumazet@...gle.com>,
	<pabeni@...hat.com>, <andrew+netdev@...n.ch>, <horms@...nel.org>,
	<shuah@...nel.org>, <willemb@...gle.com>, <petrm@...dia.com>,
	<donald.hunter@...il.com>, <michael.chan@...adcom.com>,
	<pavan.chebbi@...adcom.com>, <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH net-next 6/9] selftests: drv-net: gro: use SO_TXTIME to
 schedule packets together


Jakub Kicinski <kuba@...nel.org> writes:

> Longer packet sequence tests are quite flaky when the test is run
> over a real network. Try to avoid at least the jitter on the sender
> side by scheduling all the packets to be sent at once using SO_TXTIME.
> Use hardcoded tx time of 5msec in the future. In my test increasing
> this time past 2msec makes no difference so 5msec is plenty of margin.
> Since we now expect more output buffering make sure to raise SNDBUF.
>
> Experimenting with long sequences I see frequent failures when sending
> 200 packets, only 50-100 packets get coalesced. With this change
> up to 1000 packets get coalesced relatively reliably.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>

Reviewed-by: Petr Machata <petrm@...dia.com>