netdev - Re: [Intel-wired-lan] [PATCH iwl-next v2] igc: Get rid of spurious interrupts

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Message-ID: <6404e140-f6b2-4a55-a4e0-af9d9db4f875@intel.com>
Date: Tue, 23 Jul 2024 09:29:52 +0300
From: Mor Bar-Gabay <morx.bar.gabay@...el.com>
To: Kurt Kanzenbach <kurt@...utronix.de>, Jesse Brandeburg
	<jesse.brandeburg@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>
CC: Maciej Fijalkowski <maciej.fijalkowski@...el.com>, Vinicius Costa Gomes
	<vinicius.gomes@...el.com>, <netdev@...r.kernel.org>, "Sebastian Andrzej
 Siewior" <bigeasy@...utronix.de>, Eric Dumazet <edumazet@...gle.com>,
	<intel-wired-lan@...ts.osuosl.org>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH iwl-next v2] igc: Get rid of spurious
 interrupts

On 21/06/2024 9:56, Kurt Kanzenbach wrote:
> When running the igc with XDP/ZC in busy polling mode with deferral of hard
> interrupts, interrupts still happen from time to time. That is caused by
> the igc task watchdog which triggers Rx interrupts periodically.
> 
> That mechanism has been introduced to overcome skb/memory allocation
> failures [1]. So the Rx clean functions stop processing the Rx ring in case
> of such failure. The task watchdog triggers Rx interrupts periodically in
> the hope that memory became available in the mean time.
> 
> The current behavior is undesirable for real time applications, because the
> driver induced Rx interrupts trigger also the softirq processing. However,
> all real time packets should be processed by the application which uses the
> busy polling method.
> 
> Therefore, only trigger the Rx interrupts in case of real allocation
> failures. Introduce a new flag for signaling that condition.
> 
> [1] - https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3be507547e6177e5c808544bd6a2efa2c7f1d436
> 
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> Acked-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
> Reviewed-by: Simon Horman <horms@...nel.org>
> ---
> Changes in v2:
> - Index Rx rings correctly
> - Link to v1: https://lore.kernel.org/r/20240611-igc_irq-v1-1-49763284cb57@linutronix.de
> ---
>   drivers/net/ethernet/intel/igc/igc.h      |  1 +
>   drivers/net/ethernet/intel/igc/igc_main.c | 30 ++++++++++++++++++++++++++----
>   2 files changed, 27 insertions(+), 4 deletions(-)
> 
Tested-by: Mor Bar-Gabay <morx.bar.gabay@...el.com>