From patchwork Thu Feb 29 18:17:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 13577542 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 2C6A137A; Thu, 29 Feb 2024 18:31:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709231489; cv=none; b=WNyW8Z8kx5FaFAISlcsTZZLL9pyRMTu6j4WEonh0yJ3/tPMbvUe+SK3mzdF68bICG5A7PufZXO6oCVbJGpxCWw7RY3cVX+VD5TAKScgyzUF740s5j58PttC8O2gMsjAI8BuEHgkUpoi6DDUiDrxTIbUEVlsL7h14bhEyjNr8vI4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709231489; c=relaxed/simple; bh=kVQBBG8K+hDcFi7OSyJAb1VmE5J43rZTZM807TYsBKA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=BMLaaiLKVircJ2dp8DDiIE8H1YhjevSbFfA5FehfaiNGZRheWdA0BFQuTpl2cztkvIuM1tZwQ6xAtEs0J97TdFVAgCODZPn4OxyqvO/S26bakV4HvfRl19H1E0titjo5CWtArDdjummVuLaQNxB3uyRddebXYhHzHpVDO5hTmdU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=l8mPdTAS; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=VBN3PkA9; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="l8mPdTAS"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="VBN3PkA9" From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1709231486; 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=2ghJABFM1TMIbzRqLTziilHNZM/la1mEMF6DVsm8KTY=; b=l8mPdTASf6JTitOVtaeF/6Ea9NFJgZ+zLcUzrQvkPx09S3GD6DTWUnYkR8EW1HIj02PpO4 Xvlz9e233YrpVYmmXEqvVuVJbNW1/nlFJU3RYNTUhDU4HocoX2MivDNKZc+rPI0i8/S40g 8D8TraiA446cR0f3vrWp5PCBe67AQ6l4BwEb/fqKEoN0HgyVZZ8dn1jFQ5GfPKtAgaFD4j CyXKzo4504Q6OX9tUW6QE7vNAp2496L2aspt/lS48VecVVS5ayG4LSO54B7ctc5W1BOCFr zrx4rFSVzE33234V1YEbDd9ZXWaKVTl/jDv4uGT1Iz6nrXrUxu6ZLlw2FmpYSg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1709231486; 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=2ghJABFM1TMIbzRqLTziilHNZM/la1mEMF6DVsm8KTY=; b=VBN3PkA9k94JvHmpHEk+qjVGEUQ37tkg1ToHf9ABvlC1Q56uUU9rmXJXqvCZhT9Ai/XfPI tGKKVOhLJ3nwmqBA== To: bpf@vger.kernel.org, netdev@vger.kernel.org Cc: =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , "David S. Miller" , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eric Dumazet , Hao Luo , Jakub Kicinski , Jesper Dangaard Brouer , Jiri Olsa , John Fastabend , Jonathan Lemon , KP Singh , Maciej Fijalkowski , Magnus Karlsson , Martin KaFai Lau , Paolo Abeni , Peter Zijlstra , Song Liu , Stanislav Fomichev , Thomas Gleixner , Yonghong Song Subject: [PATCH RFC v2 net-next 0/2] Use per-task storage for XDP-redirects on PREEMPT_RT Date: Thu, 29 Feb 2024 19:17:54 +0100 Message-ID: <20240229183109.646865-1-bigeasy@linutronix.de> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC In [0] I introduced explicit locking for resources which are otherwise locked implicit locked by local_bh_disable() and this protections goes away if the lock in local_bh_disable() is removed on PREEMPT_RT. There was a big complained once it came to the locking of XDP related resources during XDP-redirect because it was mostly per-packet and the locking, even not contended, was seen as a problem [1]. Another XDP related problem was that I also touched every NIC-driver using XDP. This complicated the "how to write a NIC driver" further. To solve both problems I was thinking about an alternative and ended up with moving the data structure from per-CPU to per-task on PREEMPT_RT. Instead of adding it to task_struct, I added a pointer there and setup the struct on stack. In my debug build on x86-64 the struct bpf_xdp_storage has 112 bytes and collected the per-CPU ressources. I've been benchmark the outcome on !RT. I meassured 14,880,077 pkt/s with pktgen + "xdp-bench drop" on a ixgbe which is the interface limit. I then lowered the clockspeed of the CPU (on the RX side) and received approx between 12,156,279 and 12,476,759 pkt/s. The results were not consistent and varied between runs mostly in that range with and without the patches. v1…v2 https://lore.kernel.org/all/20240213145923.2552753-1-bigeasy@linutronix.de - Renamed the container struct from xdp_storage to bpf_net_context. Suggested by Toke Høiland-Jørgensen. - Use the container struct also on !PREEMPT_RT builds. Store the pointer to the on-stack struct in a per-CPU variable. Suggested by Toke Høiland-Jørgensen. I'm posting here only two patches which replace the XDP redirect part (patches 14 to 24) from the original series. [0] https://lore.kernel.org/all/20231215171020.687342-1-bigeasy@linutronix.de/ [1] https://lore.kernel.org/all/CAADnVQKJBpvfyvmgM29FLv+KpLwBBRggXWzwKzaCT9U-4bgxjA@mail.gmail.com/ [2] https://lore.kernel.org/all/20231215145059.3b42ee35@kernel.org Sebastian