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[24.6.151.244]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2fa0b9c5872sm4021465a91.0.2025.02.10.10.58.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2025 10:58:08 -0800 (PST) Date: Mon, 10 Feb 2025 10:58:06 -0800 From: Joe Damato To: Kurt Kanzenbach Cc: Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Sebastian Andrzej Siewior , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org Subject: Re: [PATCH 3/3] igb: Get rid of spurious interrupts Message-ID: Mail-Followup-To: Joe Damato , Kurt Kanzenbach , Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Sebastian Andrzej Siewior , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org References: <20250210-igb_irq-v1-0-bde078cdb9df@linutronix.de> <20250210-igb_irq-v1-3-bde078cdb9df@linutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250210-igb_irq-v1-3-bde078cdb9df@linutronix.de> On Mon, Feb 10, 2025 at 10:19:37AM +0100, 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. > > Follow the same logic as in commit 8dcf2c212078 ("igc: Get rid of spurious > interrupts"). > > [1] - https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3be507547e6177e5c808544bd6a2efa2c7f1d436 > > Signed-off-by: Kurt Kanzenbach > --- > drivers/net/ethernet/intel/igb/igb.h | 3 ++- > drivers/net/ethernet/intel/igb/igb_main.c | 29 +++++++++++++++++++++++++---- > drivers/net/ethernet/intel/igb/igb_xsk.c | 1 + > 3 files changed, 28 insertions(+), 5 deletions(-) I am not an igb expert (nor do I have such a device), but after reading the source a bit this seems reasonable. I suppose perhaps a better direction in the future would be to convert the driver to the page pool, but in the meantime the proposed change seems reasonable. Reviewed-by: Joe Damato