From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48FDAC4332F for ; Tue, 31 Oct 2023 10:14:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236177AbjJaKOh (ORCPT ); Tue, 31 Oct 2023 06:14:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236182AbjJaKOe (ORCPT ); Tue, 31 Oct 2023 06:14:34 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6B1EE113; Tue, 31 Oct 2023 03:14:28 -0700 (PDT) Date: Tue, 31 Oct 2023 11:14:24 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1698747266; 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: in-reply-to:in-reply-to:references:references; bh=iX/KH2uQ59JkXmBYik5taBnOlkDyh5K27ne0UO08DGU=; b=d4LB31sE1eHw2NCSlos+jWEyMRnRlJzazcmVO7Td+52CglmICB8no/Ax9If8y37tHYIagB jlPIXg8buAenKvW5FjLSkL9197SERdIMwvwye2I5rxz4p6ClJL4P50kTfobmpPqZ+Xy1zL OdnHdmpsmTYDRU9bD6vVutayqkKKdq9jWaAPrvI13CEzCWiHsEUQQFODPX3T/tnBbiOTqE oq4TWRpIOyyKxtoWAr3nrt2dacFvYVLGTy9zeiBNNRwttPJ35zQmYFUi0y7o8LeYizrBeX TEjFunK61uz4NcOG6J+4J4UHNTblde8USIObjPWnIl1NdDT02yiCRbCFPtoPPQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1698747266; 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: in-reply-to:in-reply-to:references:references; bh=iX/KH2uQ59JkXmBYik5taBnOlkDyh5K27ne0UO08DGU=; b=ziqUWti5quLNaYI35IOsIj84QXu9EEltRruBzXDw6AP4k7Efux/puGFxvYh2y/wOIdrun+ ImCCo34RWCha9OCA== From: Sebastian Andrzej Siewior To: Jakub Kicinski , Wander Lairson Costa , juri.lelli@redhat.com Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Paolo Abeni , Peter Zijlstra , Thomas Gleixner , Come On Now Subject: Re: [PATCH net-next 0/2] net: Use SMP threads for backlog NAPI (or optional). Message-ID: <20231031101424.I2hTisNY@linutronix.de> References: <20230929162121.1822900-1-bigeasy@linutronix.de> <20231004154609.6007f1a0@kernel.org> <20231007155957.aPo0ImuG@linutronix.de> <20231009180937.2afdc4c1@kernel.org> <20231016095321.4xzKQ5Cd@linutronix.de> <20231016071756.4ac5b865@kernel.org> <20231016145337.4ZIt_sqL@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231016145337.4ZIt_sqL@linutronix.de> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-10-16 16:53:39 [+0200], To Jakub Kicinski wrote: > On 2023-10-16 07:17:56 [-0700], Jakub Kicinski wrote: > > On Mon, 16 Oct 2023 11:53:21 +0200 Sebastian Andrzej Siewior wrote: > > > > Do we have reason to believe nobody uses RPS? > > > > > > Not sure what you relate to. I would assume that RPS is used in general > > > on actual devices and not on loopback where backlog is used. But it is > > > just an assumption. > > > The performance drop, which I observed with RPS and stress-ng --udp, is > > > within the same range with threads and IPIs (based on memory). I can > > > re-run the test and provide actual numbers if you want. > > > > I was asking about RPS because with your current series RPS processing > > is forced into threads. IDK how well you can simulate the kind of > > workload which requires RPS. I've seen it used mostly on proxyies > > and gateways. For proxies Meta's experiments with threaded NAPI show > > regressions across the board. So "force-threading" RPS will most likely > > also cause regressions. > > Understood. > > Wandere/ Juri: Do you have any benchmark/ workload where you would see > whether RPS with IPI (now) vs RPS (this patch) shows any regression? So I poked offlist other RH people and I've been told that they hardly ever test RPS since the NICs these days have RSS in hardware. Sebastian