From mboxrd@z Thu Jan 1 00:00:00 1970 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 1DC1628DBA for ; Mon, 16 Oct 2023 14:53:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="08pEtaXT"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="/SJFTM2f" Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A221AB; Mon, 16 Oct 2023 07:53:41 -0700 (PDT) Date: Mon, 16 Oct 2023 16:53:37 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1697468019; 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=kYxGWux4bz1oifYiW1ESfMnhECuBhrHUbAQIAzCsCdk=; b=08pEtaXTRgkjC5/In32LsLPPD1O/UMtjzGU3yQbKnybq0ffF1HWcJJSjJQ+e+jU1a4YlW/ hknEptlxGFu/DVVItuh+hgpEowWjIuqGuAFBS9l11L+oIXHjXHbr/CPA41RXSGWV89ub9B 2ak0ggP3XdjI/CAUsOpxtigupxXn5Fv1/aWYIEhjtfnJNph9b0uv3iW4YRB/3sV8kbxOHM B6ybeDJzvdvMWesGxnSc6ZJP0FQzJE1BgWh/K5wI5BO7NeBIcQ+IR4zMusGe/we0rPycts JgGZq+iDpVNIR3adchWnrgFHRwey5pFMbJ3CUbGOAy61nQdoimv6G7XIGp8UYg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1697468019; 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=kYxGWux4bz1oifYiW1ESfMnhECuBhrHUbAQIAzCsCdk=; b=/SJFTM2fCbawcyZjIS46roZClWxcsl/WYkcyBiBYwergMh5/z2qQ9OQLjwxZJx1Kmb7PIU jhFqf5qDSa1ocgAA== 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: <20231016145337.4ZIt_sqL@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> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20231016071756.4ac5b865@kernel.org> 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 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? Sebastian