From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCHv1 net] xen-netback: require fewer guest Rx slots when not using GSO Date: Thu, 10 Sep 2015 10:41:40 +0100 Message-ID: <55F15054.1070003@citrix.com> References: <1441718714-3256-1-git-send-email-david.vrabel@citrix.com> <20150909193416.GA15048@l.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Cc: , , Wei Liu , Ian Campbell To: Konrad Rzeszutek Wilk Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:23548 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750741AbbIJJlo (ORCPT ); Thu, 10 Sep 2015 05:41:44 -0400 In-Reply-To: <20150909193416.GA15048@l.oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: On 09/09/15 20:34, Konrad Rzeszutek Wilk wrote: > On Tue, Sep 08, 2015 at 02:25:14PM +0100, David Vrabel wrote: >> Commit f48da8b14d04ca87ffcffe68829afd45f926ec6a (xen-netback: fix >> unlimited guest Rx internal queue and carrier flapping) introduced a >> regression. >> >> The PV frontend in IPXE only places 4 requests on the guest Rx ring. > > in IPXE ? What is that? ipxe.org >> Since netback required at least (MAX_SKB_FRAGS + 1) slots, IPXE could >> not receive any packets. >> >> a) If GSO is not enabled on the VIF, fewer guest Rx slots are required >> for the largest possible packet. Calculate the required slots > > s/slots/slot number/ >> based on the maximum GSO size or the MTU. >> >> This calculation of the number of required slots relies on >> 1650d5455bd2 (xen-netback: always fully coalesce guest Rx packets) >> which present in 4.0-rc1 and later. >> >> b) Reduce the Rx stall detection to checking for at least one > > s/to/by/ >> available Rx request. This is fine since we're predominately >> concerned with detecting interfaces which are down and thus have >> zero available Rx requests. > > s/have zero available Rx requests/no available Rx requests/? If the only review comments you have are unnecessary changes to the grammar in the commit message, it's probably best if you don't post them. David