From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f175.google.com (mail-pf0-f175.google.com [209.85.192.175]) by dpdk.org (Postfix) with ESMTP id 75D717CCE for ; Thu, 1 Jun 2017 20:00:19 +0200 (CEST) Received: by mail-pf0-f175.google.com with SMTP id e193so33760634pfh.0 for ; Thu, 01 Jun 2017 11:00:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=IcRTfRptbUCI8sV5/IGlEQjVHLxmff9Qf4VFVaWLm28=; b=ObXFrXaV4DIq89A5hfkEuJHpKoLZolSXVFI9itKY3g8KmX/tcHf7qlEg86k4qA5fiB dIr3krhNJfaX8lFzmkQSXD3bXI+L8Py7VhGjX0PnfUIePkvL1cICRpzs95uLb6EZgWPJ DJhz5WsHUx10n6zOkVCigOovvya3Knihwa09mNYeOIIDzmHVzCHByoEZkjaQdbP5h+S1 h0EUwXhhTUoOX5ktZg0m4Axy8eV+61c7hjfbhqd2r4lXEKnxEIOmwxPXtXUHAQtq273d F7aEMfJewLgG0kK0HawHDMkJgSOUsRqu1NlU1keFzQD102mgQPa7o9Obdi5am65VVS8D uRRQ== 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=IcRTfRptbUCI8sV5/IGlEQjVHLxmff9Qf4VFVaWLm28=; b=VbIZ0b7Jj9FGz5Ej0jzRr8kGjdyZJsPqRUFjVJ3VoZWL9wRLV9g00AieChMM14i5ON 8zlDZtFNhmoxHpvtgQWITelGUXSO21vUsv1zRN9lDqsgOhE1gPRTEquqbdyrIiwDSgtW BJgebQMMvBP4KrUG3qc3VXL6K7S+pOLWjzuwsm9+NGcywKlHAn05sH8KNYYs/wbRqI75 EFeZJeU5rKHnKQOf9X9jPA0tKeb/SSzc07sc5xGb3PLbHP9rIeXztuxzMZYPl0BO3Zzh uLYxeFX3hc595yFUTo5YFMdAWA+jiuC1is54d0Vx71TZvK1IBcgtPK09xcPAN7K13UDe cSyw== X-Gm-Message-State: AODbwcBYguOZGKBP5oP9zy+SaBJHKa+olNPLAO79lDlSDOEb16C5sFke mygnPxsRKfFOS1e3YyoA1w== X-Received: by 10.98.65.26 with SMTP id o26mr2225599pfa.228.1496340017035; Thu, 01 Jun 2017 11:00:17 -0700 (PDT) Received: from xeon-e3 (76-14-207-240.or.wavecable.com. [76.14.207.240]) by smtp.gmail.com with ESMTPSA id e124sm30746523pgc.17.2017.06.01.11.00.16 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 01 Jun 2017 11:00:16 -0700 (PDT) Date: Thu, 1 Jun 2017 11:00:10 -0700 From: Stephen Hemminger To: =?UTF-8?B?R2HDq3Rhbg==?= Rivet Cc: dev@dpdk.org Message-ID: <20170601110010.79a147c2@xeon-e3> In-Reply-To: <20170601141241.GC18840@bidouze.vm.6wind.com> References: <6b96432155ffd2d5fc6f6011a0b229c2224116f8.1496065002.git.gaetan.rivet@6wind.com> <20170531081526.3e8de246@xeon-e3> <20170601141241.GC18840@bidouze.vm.6wind.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [dpdk-dev] [PATCH v4 05/12] net/failsafe: add plug-in support X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Jun 2017 18:00:19 -0000 On Thu, 1 Jun 2017 16:12:41 +0200 Ga=C3=ABtan Rivet wrote: > On Wed, May 31, 2017 at 08:15:26AM -0700, Stephen Hemminger wrote: > > On Mon, 29 May 2017 15:42:17 +0200 > > Gaetan Rivet wrote: > > =20 > > > Periodically check for the existence of a device. > > > If a device has not been initialized and exists on the system, then it > > > is probed and configured. > > >=20 > > > The configuration process strives to synchronize the states between t= he > > > plugged-in sub-device and the fail-safe device. =20 > >=20 > > There are existing event models (udev and netlink) that could be used to > > do plug-in support without polling. Polling relies on application doing > > rte_alarms and many don't. =20 >=20 > Indeed. This possibility arose during development. >=20 > The main issue with it however is that it introduces an asynchronous > design, which the DPDK and PMDs underneath are not well-suited to > interact with. It goes against the grain in a way. >=20 > The polling is simple. It can work with all models of device and is > independent of event models specific to any architecture. >=20 > It also allows to simplify the contexts in which probing and > removal are done. Currently there is only one, the interrupt thread. > This solves a few possible race conditions without having to resort to > critical sections. >=20 > The only dependency is on another DPDK subsystem, rte_alarm. > I used alarms here because rte_timers need regular rte_timer_manage() > calls and there is little way to guarantee the frequency of the calls. >=20 > rte_alarms do not force any externalities on applications, thus allowing a > seamless use of the fail-safe. >=20 The issue with rte_alarm and also with LSC interrupt callbacks is that they don't run on a normal DPDK EAL application thread. These callbacks run on a DPDK internal pthread. I remember having to do some application hacks like having the callback generate an internal event on a pipe.