From patchwork Tue Mar 19 20:44:37 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yan Zhai X-Patchwork-Id: 13597052 X-Patchwork-Delegate: kuba@kernel.org Received: from mail-qt1-f179.google.com (mail-qt1-f179.google.com [209.85.160.179]) (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 851A93FBA3 for ; Tue, 19 Mar 2024 20:44:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.179 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710881084; cv=none; b=cBI6oW5U/wJwULUWQEYAdIIAMXfmYAHIqK+PkV/I7vrmfhjEmcHyBze+bHMOH/ZfSrEabi06xXav892L5q8hDs4JYgUy2cLDjlkrNqGmKQVWftdZ5sw8dRtAUbuNdYsRH2pQlmHf5O9aO1uzOAz/QwIP+NDGzOISzYx0D32zewI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710881084; c=relaxed/simple; bh=lIO9MabCA0Vp4l3RyBQKLB7GagIDesVLqRMDYikDatA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VJZglNnfPVAgay08GbPTpgp17V726wZ0TTbFbUn9Hgf8zPITF7v69lP6WEkYQjTi7fhQoZIrFY0PHOFKR6u4s0UtdXNNCiU/vKzx0u4pqh3uOvCx/P0iNhY+5IpBs+Ig7sj+dENEhPUdnHKoENsFxJJ0LDDLzFEtGbFCzm8LCOM= 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=HCAA8OEY; arc=none smtp.client-ip=209.85.160.179 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="HCAA8OEY" Received: by mail-qt1-f179.google.com with SMTP id d75a77b69052e-430baec7bb5so2766601cf.0 for ; Tue, 19 Mar 2024 13:44:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google09082023; t=1710881080; x=1711485880; 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=VcyYWRaJ2z9OCo3//n/tTkrj0ma4Eol6nlX2m3ez4hs=; b=HCAA8OEYnfyjXPN2g/n0nTxMowCW9mbg6CmydUQ4bRuoUnuFFjOGSe7LQBcrPfVCfo O66rE/8zgWpIJpaOa3Sq+UhcGgXJ8m0MpKrQuuknWJ4oCXcMR8+RGly5ALckHNlubq/A 3imWG14J7mdr1txJbwWOxf/G1VJXAsNkGYW3/Y1BvDEhytt4RZ8G75qa09HIHpz+mOIS KlyE0+eCY68tqAyxdvT2yzzjl1XSWGtD00xXOwuBDHrdr0ve8mMC2+1rOVhKxuYrgB7K ZmbZ47+/QWKD+AFC8NSvtJ/0JVlW01OCOSplfV0JulmAm408jLy7fWSn8VOutYm+ajyv dMmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710881080; x=1711485880; 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=VcyYWRaJ2z9OCo3//n/tTkrj0ma4Eol6nlX2m3ez4hs=; b=DwEIzEShgaZKFcF6NncexVxG8kXj+GwVlraPFdjwPtOGdTx98rUf4VJ78t+lsrjPPa i2GTSfQx/PwXmkEoVAu2I4nUT2/p58Tyg3uYQVb7a0yTpCy+yT+rlp0d8IHg0MpOF14a 6/RIfxOCzBv8OZPXZGSlousLkPEeqweHVK/TBCCpLoecLY2od0bxxxUo2n7NP5GpfkvW MwMFzj/3loCFbVsarzh/zAFHaS4FuYwEXCjGkqmoWNxq0WYLTMlMIK8LDZExDzS0bQdg GEbJJOAD1gpESTrc3xo8Z5VBh9Yurk5bUW/enXLTSGcyXNhixg3WQrxdJUuDML0m07dM p+bg== X-Forwarded-Encrypted: i=1; AJvYcCVFeIK45elak4q3s06L7Q7CYqJxOAO+J3Mi8+K9UGubTy8jOVrqyX3e509paVZpfesc0X+DoJfo98wfEi+1tgVRq3Fi X-Gm-Message-State: AOJu0Yzcqkd1ykn98WwkaFVpCBP7yIVcp3w+cbpF2/rl6D3VH+xhdcfu o79MY3UhHP+eEySrRlFPz7S9uRKtQT76B7xsMQCfiscuCK3H6JUTt1ZwfKv605g= X-Google-Smtp-Source: AGHT+IEqJqSfTz5bjyf6+FFNUXSLrbwrdMDLWUdtYJ2krdBAfEjY8Q3lzIBNIXbpm1TJn+LzQI6kHw== X-Received: by 2002:a05:6214:14b0:b0:691:3cf5:b7ad with SMTP id bo16-20020a05621414b000b006913cf5b7admr1034118qvb.12.1710881080537; Tue, 19 Mar 2024 13:44:40 -0700 (PDT) Received: from debian.debian ([2a09:bac5:7a49:1cd2::2df:49]) by smtp.gmail.com with ESMTPSA id pn4-20020a056214130400b006961c1d2b6fsm2822954qvb.80.2024.03.19.13.44.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Mar 2024 13:44:40 -0700 (PDT) Date: Tue, 19 Mar 2024 13:44:37 -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 , 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 , Sebastian Andrzej Siewior Subject: [PATCH v5 net 2/3] net: report RCU QS on threaded NAPI repolling Message-ID: <4c3b0d3f32d3b18949d75b18e5e1d9f13a24f025.1710877680.git.yan@cloudflare.com> References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Patchwork-Delegate: kuba@kernel.org 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 Acked-by: Paul E. McKenney --- 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 303a6ff46e4e..9a67003e49db 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6743,6 +6743,8 @@ static int napi_threaded_poll(void *data) void *have; while (!napi_thread_wait(napi)) { + unsigned long last_qs = jiffies; + for (;;) { bool repoll = false; @@ -6767,6 +6769,7 @@ static int napi_threaded_poll(void *data) if (!repoll) break; + rcu_softirq_qs_periodic(last_qs); cond_resched(); } }