From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5FCEEC76195 for ; Wed, 17 Jul 2019 20:19:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F1A5A21849 for ; Wed, 17 Jul 2019 20:19:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qln0DjeK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727639AbfGQUTb (ORCPT ); Wed, 17 Jul 2019 16:19:31 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:35104 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725993AbfGQUTa (ORCPT ); Wed, 17 Jul 2019 16:19:30 -0400 Received: by mail-wm1-f67.google.com with SMTP id l2so23392185wmg.0; Wed, 17 Jul 2019 13:19:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=nqaMPv708RCiesrxZDz1cZrIB3dLCSSINVU8+So70w0=; b=qln0DjeKwd94XPAiTvY1WJ/CL7tTNBmdoL8p2i+aj2tj2RtVTVZWjR2Rb+16c1e1Kh jMlXYQBkLVc7H6+Fc44QHiGsKIibSnZ+IzbOj9/4EFAoPHu/A5Lv8MCPIaGpHW3j7+Xk 6KHi3NJPjbBkDcZq3qMJkzna6/7asPVRyLLCIO1Xy2/yPL5DKHBaHRmLODzVhx3HZkpJ l5IrZn7PXCb5LL+8Fz5Tn7WqQhxHctBNeUIehZqVXkS8pRpuo6Rpql0j8SwmCjeWvPJv u3DrSsUnjGFSE7M/ACJGdn9+QoJjNRSI1tVc/mRWiGjT3hci2WzLTK4jYaCQ+FBGS4SP Z+MA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=nqaMPv708RCiesrxZDz1cZrIB3dLCSSINVU8+So70w0=; b=ibwmWH81ELSumkwW9w8un5wNhEPVEl/k2IDcK08z/wi0hgDn1fnx+EwNSSIv6oIsto l+rpZ2Qq2iBXAqemQUIuJ/FGbXQZVo/gFStjBGvz/Wt5r2louYrWP3ySmVkhdYHUDYiS 8rTHwtuv5KbWeOKJk61DzSk/qO93JIuOrXzM5HGofDBeEy19FfISwYT/oSiK9DLqNXxb rXgnqKOgTv7G4WmW2V0rSdrjQOgLZmTAlHHpoUvkYWsjSsBerAOXvKGOXQdejvMd9oU2 liq6eXy6YTRPF8Ux1RV0eVSR3xGk6yA58BTtPglUOXWWsUYkXABt1oSqvdgeT3wrfJua yyig== X-Gm-Message-State: APjAAAVI+l2t2wkWvu/cs3ONpayHGqHU28un0rT0tv96NkpMbZCT5efN 1kBSfiJbjHBFH9XzLXP2s+E= X-Google-Smtp-Source: APXvYqwK1dsG8qqPpVwTplC7CW84CZEZ0F4XKUlx8chgxaOXxW7ZmkQrifWn4fhsWl8GynTuyQJ6EA== X-Received: by 2002:a1c:b146:: with SMTP id a67mr37260276wmf.124.1563394768433; Wed, 17 Jul 2019 13:19:28 -0700 (PDT) Received: from debian ([78.40.148.180]) by smtp.gmail.com with ESMTPSA id y1sm20423638wma.32.2019.07.17.13.19.27 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 17 Jul 2019 13:19:27 -0700 (PDT) Date: Wed, 17 Jul 2019 21:19:25 +0100 From: Sudip Mukherjee To: peterz@infradead.org, davem@davemloft.net Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: regression with napi/softirq ? Message-ID: <20190717201925.fur57qfs2x3ha6aq@debian> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20170113 (1.7.2) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi All, I am using v4.14.55 on an Intel Atom based board and I am seeing network packet drops frequently on wireshark logs. After lots of debugging it seems that when this happens softirq is taking huge time to start after it has been raised. This is a small snippet from ftrace: <...>-2110 [001] dNH1 466.634916: irq_handler_entry: irq=126 name=eth0-TxRx-0 <...>-2110 [001] dNH1 466.634917: softirq_raise: vec=3 [action=NET_RX] <...>-2110 [001] dNH1 466.634918: irq_handler_exit: irq=126 ret=handled ksoftirqd/1-15 [001] ..s. 466.635826: softirq_entry: vec=3 [action=NET_RX] ksoftirqd/1-15 [001] ..s. 466.635852: softirq_exit: vec=3 [action=NET_RX] ksoftirqd/1-15 [001] d.H. 466.635856: irq_handler_entry: irq=126 name=eth0-TxRx-0 ksoftirqd/1-15 [001] d.H. 466.635857: softirq_raise: vec=3 [action=NET_RX] ksoftirqd/1-15 [001] d.H. 466.635858: irq_handler_exit: irq=126 ret=handled ksoftirqd/1-15 [001] ..s. 466.635860: softirq_entry: vec=3 [action=NET_RX] ksoftirqd/1-15 [001] ..s. 466.635863: softirq_exit: vec=3 [action=NET_RX] So, softirq was raised at 466.634917 but it started at 466.635826 almost 909 usec after it was raised. If I move back to v4.4 kernel I still see similar behaviour but the maximum delay I get is in the range of 500usec. But if I move back to v3.8 kernel I can see there is no packet loss and the maximum delay between softirq_raise and irq_handler_entry is 103usec. Is this a known issue? Will really appreciate your help in this problem. -- Regards Sudip