From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: netif_tx_disable and lockless TX Date: Tue, 30 May 2006 23:26:26 -0700 (PDT) Message-ID: <20060530.232626.00456312.davem@davemloft.net> References: <20060531045811.GA6977@gondor.apana.org.au> <20060530.221117.85394939.davem@davemloft.net> <20060531051451.GA7110@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: mchan@broadcom.com, jgarzik@pobox.com, netdev@vger.kernel.org Return-path: Received: from dsl027-180-168.sfo1.dsl.speakeasy.net ([216.27.180.168]:24793 "EHLO sunset.sfo1.dsl.speakeasy.net") by vger.kernel.org with ESMTP id S1751292AbWEaG0O (ORCPT ); Wed, 31 May 2006 02:26:14 -0400 To: herbert@gondor.apana.org.au In-Reply-To: <20060531051451.GA7110@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Herbert Xu Date: Wed, 31 May 2006 15:14:51 +1000 > On Tue, May 30, 2006 at 10:11:17PM -0700, David Miller wrote: > > > > It will come back when net channels arrive :-) This is because net > > channel drivers will do all the work in hard IRQs and not in a NAPI or > > NAPI-like context. > > I thought the current channel stuff is RX only. Is TX completion moving > to IRQ context as well? I don't think it will be worthwhile to keep NAPI around just for TX completion. Sure the dev_kfree_skb() will schedule software interrupt work to do the actual free, but the TX ring walking and dev_kfree_skb() calls will be in hard IRQ context. > > The only regret I have about that is we will go back to not being able > > to profile ->hard_start_xmit() very well in such drivers. > > Can you elborate on that? I think I've already removed all references > to this in my memory :) If you disable IRQs in the ->hard_start_xmit() handler, you don't get timer based profiling ticks. Currently we do.