From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752544AbbKKQVG (ORCPT ); Wed, 11 Nov 2015 11:21:06 -0500 Received: from shards.monkeyblade.net ([149.20.54.216]:48552 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752603AbbKKQVC convert rfc822-to-8bit (ORCPT ); Wed, 11 Nov 2015 11:21:02 -0500 Date: Wed, 11 Nov 2015 11:20:56 -0500 (EST) Message-Id: <20151111.112056.1931193644379757340.davem@davemloft.net> To: mans@mansr.com Cc: romieu@fr.zoreil.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, slash.tmp@free.fr Subject: Re: [PATCH v5] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller From: David Miller In-Reply-To: References: <20151110.211121.422193831316296487.davem@davemloft.net> X-Mailer: Mew version 6.6 on Emacs 24.5 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 11 Nov 2015 08:21:01 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Måns Rullgård Date: Wed, 11 Nov 2015 12:22:28 +0000 > David Miller writes: > >> From: Måns Rullgård >> Date: Wed, 11 Nov 2015 00:40:09 +0000 >> >>> When the DMA complete interrupt arrives, the next chain should be >>> kicked off as quickly as possible, and I don't see why that would >>> benefit from being done in napi context. >> >> NAPI isn't about low latency, it's about fairness and interrupt >> mitigation. >> >> You probably don't even realize that all of the TX SKB freeing you do >> in the hardware interrupt handler end up being actually processed by a >> scheduled software interrupt anyways. >> >> So you are gaining almost nothing by not doing TX completion in NAPI >> context, whereas by doing so you would be gaining a lot including >> more simplified locking or even the ability to do no locking at all. > > TX completion is separate from restarting the DMA, and moving that to > NAPI may well be a good idea. Should I simply napi_schedule() if the > hardware indicates TX is complete and do the cleanup in the NAPI poll > function? ... just like every other high end driver... Yes.