From patchwork Fri Sep 29 16:20:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13404600 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 31AB1747B for ; Fri, 29 Sep 2023 16:21:32 +0000 (UTC) Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4F9421A4; Fri, 29 Sep 2023 09:21:30 -0700 (PDT) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1696004487; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=Pfy40HfW0rOpJbLp9/b9G4Tw0KUOebfRdechmC+0mdA=; b=wLXAzFm9DNE3IK001s6BGy7aX+uVYsoCxDrs2NGf9JxmjkU3JAP1YPr2HQNcV3oE0anECk LEJfB4+lBmB9VokpzPfSCqyiB9bJ76FKghCNOhWTzyqdFaX6FwwCRPmHFMJaiHoATUsmIa P/9tEcHa8m/ZVcQxcaLhrFkBTKDgc2r4iD2fBrVO/v2JYdMGqQTgP2zASBMK81mXuIAFTL 8R0cMdOc6w4iAOGYS/gwm5OdzkfrNzCq8SQew54zkH6MHCorPBQcDjyqUiTwAE0REUD4xQ ExZPnP2VL9co2HGLiyEqtA3xe5eNsxVsbUnB6D57b8hvJSfTSaqml6/auWydfg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1696004487; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=Pfy40HfW0rOpJbLp9/b9G4Tw0KUOebfRdechmC+0mdA=; b=PdNwR8qu/XS8Uos9j6mMejZBVzlKL4KAyye/CdS/ycC4jMGWhmF2WEMLYR9KjpqckLpHdq ve7nHhcR8TxoaWCw== To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Peter Zijlstra , Thomas Gleixner , Wander Lairson Costa Subject: [PATCH net-next 0/2] net: Use SMP threads for backlog NAPI (or optional). Date: Fri, 29 Sep 2023 18:20:18 +0200 Message-ID: <20230929162121.1822900-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org The RPS code and "deferred skb free" both send IPI/ function call to a remote CPU in which a softirq is raised. This leads to a warning on PREEMPT_RT because raising softiqrs from function call led to undesired behaviour in the past. I had duct tape in RT for the "deferred skb free" and Wander Lairson Costa reported the RPS case. Changes: - RFC…v1 https://lore.kernel.org/all/20230818092111.5d86e351@kernel.org - Patch #2 has been removed. Removing the warning is still an option. - There are two patches in the series: - Patch #1 always creates backlog threads - Patch #2 creates the backlog threads if requested at boot time, mandatory on PREEMPT_RT. So it is either or and I wanted to show how both look like. - The kernel test robot reported a performance regression with loopback (stress-ng --udp X --udp-ops Y) against the RFC version. The regression is now avoided by using local-NAPI if backlog processing is requested on the local CPU. Sebastian