From patchwork Fri Mar 15 19:55:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yan Zhai X-Patchwork-Id: 13593941 Received: from mail-qk1-f173.google.com (mail-qk1-f173.google.com [209.85.222.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3086054676 for ; Fri, 15 Mar 2024 19:55:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710532514; cv=none; b=q9SnqhsRLlKb+rpYyyvoavCrd3RZaN7C6mlQnL7H5CllMAdEVJlPEdd0DMiKCDHi5UZfJjoK65qabz4/6Ww9S5xagyejOTnkx4gLGlIAldUEh/uefPboJUt8+7XCXIinP3RGuFRJkT4w+bqi5bThmoSMCe2NO7ocvYQrlkCW9ZQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710532514; c=relaxed/simple; bh=9dZo3hhHILA1Vsa6/x7a9av0THiimjwMutRu9GgeKuA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=d3fZf8Fm4zoohNBq7RAWXOOqb40CWlmBDlUUN+HikPRkfQTDb+ol+9c5V5fu+wQQQZv2QSyw9RO02ldwsoOPyy/1DItacaC97xQKXecLQunu58ospVVfkb3Eum3AH8P/E4ICpXOI4/Fm3gEb79DuhQhgYkf0AQGpiC/1SpTBaY0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cloudflare.com; spf=pass smtp.mailfrom=cloudflare.com; dkim=pass (2048-bit key) header.d=cloudflare.com header.i=@cloudflare.com header.b=BcUE/iwc; arc=none smtp.client-ip=209.85.222.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cloudflare.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cloudflare.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cloudflare.com header.i=@cloudflare.com header.b="BcUE/iwc" Received: by mail-qk1-f173.google.com with SMTP id af79cd13be357-78863dc4247so106196285a.3 for ; Fri, 15 Mar 2024 12:55:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google09082023; t=1710532509; x=1711137309; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Ry29tyycjYxk6fFeMi1eD8C6LU69xTzMZ5f+WiAb3oo=; b=BcUE/iwcmxgAEyyLcpSB5a7khcC+/f/rFrXO6nFYtMUWgpgmJO4O12FN7mKbi89xvB mX9xtGcoq3YBHNj7mkbNBMhlZ2kSLwzD7h9nq2Fwr4N588iAU1j72HsCSANHuBWmi1dP px+P2PR6IPFnyq287SIEq9wAsgp+jMz06kQJv/kW5eQQ4Te2qUxyzqnARIyBGTFE3Vvl 0I4Mklxyj1thsK1AeFl82BfwY/+HlDwS05DAxge4K4dtmKIP/mXmRrln+BWVuIt0NWNi /g122hKjGVRcDXhFC56AUuu89iOZd9/z+3mx1k/8o7oN+oEEKGxCMlc8OvWQbEVGYEe+ dehA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710532509; x=1711137309; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Ry29tyycjYxk6fFeMi1eD8C6LU69xTzMZ5f+WiAb3oo=; b=eCtKmhadpQ34XBjTmolTGCkc3HQxrWfh7PfOScTY4mT+MiP3U9hwb+gPTNU2dygIwr JIHNPnhkZR6YSmiwvTsYWB0NlsS9xrDhpH8QYon2uQPYmQDwme1PTEA/8efDgrohAV3D GwUiAfMabf7uRH6DRmtbIdDeMDCD+oypC0MCpHigTAPd0raISFVkw+OIT/w7OPfIvkjH nVSGT3RCUmfHQJxSsE19xcC8vBay7gWFMIVZ6yGuFL5nnGUOGuQPiG/eEPZUhXLmChVr 9Z+U/dmtSD3yjON+dIAlLNd58v7l2fma3vYbMTLqnT4zxHWET8O+KTHtqXPZ9YeoanDO cJNA== X-Forwarded-Encrypted: i=1; AJvYcCWCjaXGZphYoTiWHJqy8+u5mv3Lfbuy8JLjhlc44ZPKgyQ9eXvKUqtiTRzgg8GI5BqAHN0wWPyPK1hwj79dShn3RXmp X-Gm-Message-State: AOJu0Yx9kRtMwNcSwsn2Z+UJLLpyIxI5/OBMbjb2RbnX/ZjUIEJYj10I gyyjJ+zTlCOycrk+RB79U+Rtl/xBksPr58SjKBWrsuBFpoyXNh52uYkyM0gvmzE= X-Google-Smtp-Source: AGHT+IFe+Jey6521uF7eX0BAurAqBmBT8HIizHqfi3SPi7OcH8reJREKFdT7IdpL5KWJ7UuCn5UH0Q== X-Received: by 2002:a05:620a:821d:b0:788:12af:3f0e with SMTP id ow29-20020a05620a821d00b0078812af3f0emr6201880qkn.56.1710532509182; Fri, 15 Mar 2024 12:55:09 -0700 (PDT) Received: from debian.debian ([2a09:bac5:7a49:1046::19f:c]) by smtp.gmail.com with ESMTPSA id h4-20020a05620a13e400b00789e94cf424sm431802qkl.108.2024.03.15.12.55.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Mar 2024 12:55:08 -0700 (PDT) Date: Fri, 15 Mar 2024 12:55:06 -0700 From: Yan Zhai To: netdev@vger.kernel.org Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jiri Pirko , Simon Horman , Daniel Borkmann , Lorenzo Bianconi , Coco Li , Wei Wang , Alexander Duyck , Hannes Frederic Sowa , linux-kernel@vger.kernel.org, rcu@vger.kernel.org, bpf@vger.kernel.org, kernel-team@cloudflare.com, Joel Fernandes , "Paul E. McKenney" , Toke =?utf-8?q?H=C3=B8iland-J?= =?utf-8?q?=C3=B8rgensen?= , Alexei Starovoitov , Steven Rostedt , mark.rutland@arm.com, Jesper Dangaard Brouer Subject: [PATCH v4 net 2/3] net: report RCU QS on threaded NAPI repolling Message-ID: <2425bc9fbfb7ef396d68d755df79dbbae48a58ab.1710525524.git.yan@cloudflare.com> References: Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: NAPI threads can keep polling packets under load. Currently it is only calling cond_resched() before repolling, but it is not sufficient to clear out the holdout of RCU tasks, which prevent BPF tracing programs from detaching for long period. This can be reproduced easily with following set up: ip netns add test1 ip netns add test2 ip -n test1 link add veth1 type veth peer name veth2 netns test2 ip -n test1 link set veth1 up ip -n test1 link set lo up ip -n test2 link set veth2 up ip -n test2 link set lo up ip -n test1 addr add 192.168.1.2/31 dev veth1 ip -n test1 addr add 1.1.1.1/32 dev lo ip -n test2 addr add 192.168.1.3/31 dev veth2 ip -n test2 addr add 2.2.2.2/31 dev lo ip -n test1 route add default via 192.168.1.3 ip -n test2 route add default via 192.168.1.2 for i in `seq 10 210`; do for j in `seq 10 210`; do ip netns exec test2 iptables -I INPUT -s 3.3.$i.$j -p udp --dport 5201 done done ip netns exec test2 ethtool -K veth2 gro on ip netns exec test2 bash -c 'echo 1 > /sys/class/net/veth2/threaded' ip netns exec test1 ethtool -K veth1 tso off Then run an iperf3 client/server and a bpftrace script can trigger it: ip netns exec test2 iperf3 -s -B 2.2.2.2 >/dev/null& ip netns exec test1 iperf3 -c 2.2.2.2 -B 1.1.1.1 -u -l 1500 -b 3g -t 100 >/dev/null& bpftrace -e 'kfunc:__napi_poll{@=count();} interval:s:1{exit();}' Report RCU quiescent states periodically will resolve the issue. Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support") Reviewed-by: Jesper Dangaard Brouer Signed-off-by: Yan Zhai --- v2->v3: abstracted the work into a RCU helper v1->v2: moved rcu_softirq_qs out from bh critical section, and only raise it after a second of repolling. Added some brief perf test result. v2: https://lore.kernel.org/bpf/ZeFPz4D121TgvCje@debian.debian/ v1: https://lore.kernel.org/lkml/Zd4DXTyCf17lcTfq@debian.debian/#t --- net/core/dev.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index 76e6438f4858..6b7fc42d4b3e 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6708,6 +6708,8 @@ static int napi_threaded_poll(void *data) void *have; while (!napi_thread_wait(napi)) { + unsigned long last_qs = jiffies; + for (;;) { bool repoll = false; @@ -6732,6 +6734,7 @@ static int napi_threaded_poll(void *data) if (!repoll) break; + rcu_softirq_qs_periodic(last_qs); cond_resched(); } }