From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout-02.galae.net (smtpout-02.galae.net [185.246.84.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 38B67376A17 for ; Fri, 29 May 2026 19:19:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.246.84.56 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780082354; cv=none; b=tVz7dz8pdj2HxzeWb6RvKDw4d0SZajKuJRwYWrdTrHtpwHZEz9HbDpxIEBXYtsLAKXvfZyLW0hHbVYQimI1SHSSTRFW20theDruIKB/c8dLQJ03u7rj/x+lRCqzFWxxFlDAqCSu8SzzzVLFMPUSnFhXmy3Y8AFDd9L9tiUQF9os= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780082354; c=relaxed/simple; bh=1l9kPAlL/kZWzxukLCkcVycSATc5e0pSWZyl0XMQAqI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=iKNDV4mf8tZemhPxOWbYTouWnz0L1M83LT+WZ9h1jylGR5bPGrxh+6e0RJ0qRoeJ7jngovWDdbS15hst1Q/PrkykPZ2UmcK08Ne5rCjm8PQriIWtT4uv98MC0N9B+ILPnV1ViM1cpgjM6wZt7RiZO+3XoJ8Du8/ZS1YR/PY8Sjk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=dQjXBwDu; arc=none smtp.client-ip=185.246.84.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="dQjXBwDu" Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-02.galae.net (Postfix) with ESMTPS id A1ADD1A373C; Fri, 29 May 2026 19:19:09 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 6DCD3601FA; Fri, 29 May 2026 19:19:09 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id EFE7010888650; Fri, 29 May 2026 21:19:02 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1780082348; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=3gGoxTQCbYwgT6qgZ25zkEpFpUWos5GQ0SIqBI0ohrk=; b=dQjXBwDuZouyE7/+grw336kWZP1ASkXwCJYXad7bMXkRloidLOw5V+ccfrkOgwB1wMojwQ oE9nKMpeojxTmByPAujrkwUHkoE3MuaP78vDTtidEJ2kRx6ZHRHB9ShPPQvRoRJMvRX6++ +enPFIl2lhExsWQe7o0woTYQMeuVW5Y5GnIwAm25f8/UEOcSUjmb5jFo/FwwrXOY3jm4nR 6Rz23fvZ/EBOOAq7ZHlf163TsnSzVAFJqvd4cBowEc70W74a68FGRRBc7RGAN5A0xsZkzg vGzuO8p+Ht6EPBUTS4qzJ9fAOa1mSMJUXKJClMXPQvjZgC6+TLVlv2fn4811fw== Message-ID: Date: Fri, 29 May 2026 21:19:01 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] net: stmmac: xgmac2: disable RBUE in default RX interrupt mask To: muhammad.nazim.amirul.nazle.asmade@altera.com, netdev@vger.kernel.org Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, rmk+kernel@armlinux.org.uk, Jose.Abreu@synopsys.com, linux-kernel@vger.kernel.org References: <20260529071734.27722-1-muhammad.nazim.amirul.nazle.asmade@altera.com> Content-Language: en-US From: Maxime Chevallier In-Reply-To: <20260529071734.27722-1-muhammad.nazim.amirul.nazle.asmade@altera.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 Hi, On 5/29/26 09:17, muhammad.nazim.amirul.nazle.asmade@altera.com wrote: > From: Nazim Amirul > > Enabling the RX Buffer Unavailable (RBUE) interrupt is counterproductive > and can trigger a MAC interrupt storm under heavy RX pressure. When the > DMA runs out of RX descriptors it fires RBUE continuously until software > refills the ring. > > However, RBUE is redundant: the normal RX completion interrupt (RIE) > already triggers NAPI, which processes completed descriptors and refills > the ring, causing the DMA to resume. The RBUE handler itself only sets > handle_rx - the same outcome as RIE. > > Remove RBUE from XGMAC_DMA_INT_DEFAULT_EN and XGMAC_DMA_INT_DEFAULT_RX > to prevent the interrupt storm while keeping normal RX handling intact. > > Fixes: d6ddfacd95c7 ("net: stmmac: Add DMA related callbacks for XGMAC2") > Signed-off-by: Nazim Amirul We had an opposite discussion about enabling rx buf unavailable interrupts for other DWMAC versions : https://lore.kernel.org/netdev/E1wBBaR-0000000GZHR-1dbM@rmk-PC.armlinux.org.uk/ While your patch makes sense, I think it's important to note that it'll now make the "rx_buf_unav_irq" stat (that we can query from userspace) stuck at 0 now. That's a user-visible behaviour change, for a stat that can be useful, one could consider that a uAPI change... Do you have some numbers on the perf impact you see when buffer starvation hits to see what we are gaining/losing here ? Maxime