From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 A125F42F71B for ; Mon, 6 Jul 2026 14:19:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783347565; cv=none; b=U1PSWgTZTaqeCQGU7E4mT7bx5iworr3mTdt/A4I23HB15lr/1m8NYGk1ng0OCaMt4Jjt6SWYPGfLhPK6dnORyMO67kjbAG3wsTk5qONw1uT/a5CE/iLzQ5WLB+jG/JRQhHEOMVvwivinEiKS1iUmoygCgsdZK/b2AwKoW5xcQKQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783347565; c=relaxed/simple; bh=neCBqWKXvaNRpzG8e2PqHcKw7/byanZoR6SfXW5PPJ0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Vu2x83yByriLreIKOlBtFq7rh/zCccGXzxOWnPP9UeM4NO8Y0LCsMxHCbgw3Oy6Zg4YKOU35Zu3sjFQpZ4CciNs9GtI4pQHOE0AwKdwH+O1LsQqqWEeumrGnntbsuOX4KtfrrAWwDu8ZWqm0N5KEiyW7JUcGRpn4o7sbQIZBUQo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=QwJm7X4W; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=U4FzFmER; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QwJm7X4W"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="U4FzFmER" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783347562; 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: in-reply-to:in-reply-to:references:references; bh=bW5f6W4En+s/vR6YO0+loZpKqOqgAQJyAbAU3Myb6WU=; b=QwJm7X4WEYZad8+3lwLgtkXxS1In6SOvOM7fEcg2+2ubY3p3rqbCjHuRVn5jfBoXRVEhlp Dc7MDhMqR7Swos1gsAT3FpPPrGAim93qL47yInqqU9kI/sACMYyjYZ8xdoybETIn2jIkgV U2TGXNhu6AV5Qi+w3P3tfpr4zDHkQdg= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-595-GSih1Yj3OEuiHvxks4qh5Q-1; Mon, 06 Jul 2026 10:19:21 -0400 X-MC-Unique: GSih1Yj3OEuiHvxks4qh5Q-1 X-Mimecast-MFC-AGG-ID: GSih1Yj3OEuiHvxks4qh5Q_1783347559 Received: by mail-wm1-f69.google.com with SMTP id 5b1f17b1804b1-493bf840a69so22724125e9.3 for ; Mon, 06 Jul 2026 07:19:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1783347559; x=1783952359; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=bW5f6W4En+s/vR6YO0+loZpKqOqgAQJyAbAU3Myb6WU=; b=U4FzFmERTAOelBstyXwBpI7w+3yfVD38BKJnOq0DiVw2udofMioFGeYRI0xTUtGX0n lEexrRg+8B7ly15z0Hdq8K2IntafWggD/cf/AIjz60IZTTiQf/PkhqUMLhzRV5B2pxr/ w0jY+xGiuMeQEE0y1TsLLSfjktoEzpKve5FsBBDfUQfv32S3ypbsxlIMmktADRzI4GOK YJXrL+Us/n30TrxUx0dCAP0aYV7CrfWbP+ho9tie847rqXmUuJO8F7OE27m6J7Y5qfad l6QkxUQCDVi1SsfoijCqoZ8NRK92LpX6eA01ArR0ObI+0QuEmaYFtQ6HalN3xQNn8pu+ cRSg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783347559; x=1783952359; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=bW5f6W4En+s/vR6YO0+loZpKqOqgAQJyAbAU3Myb6WU=; b=AqYuw/7hmtSPBGqK4HnTp/P/fCH+gHIUKRpfKm4iHstw4LAKRDIYhvzFCMj+6KvSQ/ zRdTL91RCliApxJy2ci8P1HV3HugcV4tjuJMqwlTdiVY3L11G45XQsF90K0jCNyT/gHS LfK5gWW0WXTabEC0zBvBwYTdraSUVLBlA6OD8t7taF0jF8LS+hpouYuXlp6giy2u4404 uATYCl46FFYmK0uu/T8jyH54zt4gvZm8jjFQZnfUME+eWSPAx76xfLPR7TPo+ZESW5Ca ARs1oixuYJ8kG3syiyjdaCvPmCDVVFMu3JZWOosFVR0kXWCeKaNv0abvZFqjDYDvkq8h De0A== X-Forwarded-Encrypted: i=1; AHgh+Rqlr4JhWYid8gcRKG13JEqwZiMdd/MmUop7Sy/+Kux8seZqYZXRDUdNIAT4/YFcvAVs/TuVm8g=@vger.kernel.org X-Gm-Message-State: AOJu0YwdAu2zV+2qf4JrOYCuJlYOvTeBuAcUkcO0/Mf5+N76BwsDCJHY ibBD8cCn5SD/UD/BniKGDyGsByaJv5whQ333ONefejIglQoT/GwEvNQJz1xFyE7TndHoPiMMjTg mAyAHzkaSk/W8YDnGwrBFY7A3Dn75Db+8/5VqUtrW1CT2MjA0e4a3ibcthQ== X-Gm-Gg: AfdE7cmPmt+yx4eJnKOH66t2GtAEK9tcAjcO86j7dG3T0k4Jun7yXiww89jnDLpeqSj 0PR3truPNZ5BYfN79U8PJj6ZtKVGraC2Kc50eIkr+VwtVvAtzo5wTPt79OPGylGjJ2FDHKeKrQr bvTpnewcPOyX4CqxGzMCVJP3s/EmkP1w4tuCakfOs7lZbQInyT2TfUufKApZiBqJAsyMzsEsmL5 QYMvm1I0T8pVN/3wZOae6rPj3VyYv8EO07Lt/9R6faTfaasnauaY/b1kNJbcbnOW/Ptnw4PriVR hLh5Ovv2/HVpBonuKbUg3i1FMRtj/aDdDBkaRx/iKRbQ57AJspD5XmtZsP6teeCY9QrFpXptQwV auf9HPbLju48UBgViMjZkcClSgf2xLU2R7wfrw3ITGznVwfTQN3IAiy9IQSOwDjT4rf49Jxc7N6 TRbantWrSqCc77 X-Received: by 2002:a05:600c:3b08:b0:493:cc25:9c0e with SMTP id 5b1f17b1804b1-493df0410d7mr9077675e9.14.1783347558985; Mon, 06 Jul 2026 07:19:18 -0700 (PDT) X-Received: by 2002:a05:600c:3b08:b0:493:cc25:9c0e with SMTP id 5b1f17b1804b1-493df0410d7mr9077035e9.14.1783347558499; Mon, 06 Jul 2026 07:19:18 -0700 (PDT) Received: from ?IPV6:2a0d:3344:5521:6b10:58fd:68f:7756:389d? ([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47a9de1d8cdsm27253314f8f.1.2026.07.06.07.19.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Jul 2026 07:19:17 -0700 (PDT) Message-ID: Date: Mon, 6 Jul 2026 16:19:16 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 net-next] net: neigh: avoid calling neigh_forced_gc on every alloc when table is full To: Vimal Agrawal , netdev@vger.kernel.org Cc: kuba@kernel.org, kuniyu@google.com, edumazet@google.com, vimal.agrawal@sophos.com References: <20260625084213.4e0b70c4@kernel.org> <20260706065813.66116-1-vimal.agrawal@sophos.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260706065813.66116-1-vimal.agrawal@sophos.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/6/26 8:58 AM, Vimal Agrawal wrote: > Once the neighbour table exceeds gc_thresh3, neigh_forced_gc() is called > on every allocation attempt with no rate limiting. In workloads with mostly > active/reachable entries, the GC walk traverses a large portion of the > neighbour table without reclaiming entries, holding tbl->lock for an > extended period. This causes severe lock contention and allocation > latencies exceeding 16ms under sustained neighbour creation. > > Add a pre-lock check in neigh_forced_gc() to skip the GC run if one was > performed within the last 50 ms, avoiding repeated full table scans and > lock acquisitions on the hot allocation path. > > Profiling of neigh_create() shows ~3 orders of magnitude latency > improvement with this change. > > Link: https://lore.kernel.org/netdev/CALkUMdSCpx_ywYCx_ePLdm6yioO1nQWx7sSM=AEgsq0kywHxTw@mail.gmail.com/ > Signed-off-by: Vimal Agrawal This apparently breaks neigh self-tests: # 29.38 [+5.12] TEST: IPv4 "extern_valid" flag: Forced garbage collection [FAIL] //... # 85.91 [+5.11] TEST: IPv6 "extern_valid" flag: Forced garbage collection [FAIL] full log at: https://netdev-ctrl.bots.linux.dev/logs/vmksft/net/results/722145/13-test-neigh-sh/ /P