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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9829DC3F68F for ; Wed, 11 Dec 2019 14:12:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64AEA2054F for ; Wed, 11 Dec 2019 14:12:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729724AbfLKOMk (ORCPT ); Wed, 11 Dec 2019 09:12:40 -0500 Received: from s3.sipsolutions.net ([144.76.43.62]:55060 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727554AbfLKOMj (ORCPT ); Wed, 11 Dec 2019 09:12:39 -0500 Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.92.3) (envelope-from ) id 1if2jB-004BxT-Uz; Wed, 11 Dec 2019 15:12:34 +0100 Message-ID: Subject: Re: iwlwifi warnings in 5.5-rc1 From: Johannes Berg To: Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= , Jens Axboe , Emmanuel Grumbach , Luca Coelho Cc: "linux-wireless@vger.kernel.org" , Networking Date: Wed, 11 Dec 2019 15:12:31 +0100 In-Reply-To: <87r21bez5g.fsf@toke.dk> References: <9727368004ceef03f72d259b0779c2cf401432e1.camel@sipsolutions.net> <878snjgs5l.fsf@toke.dk> <3420d73e667b01ec64bf0cc9da6232b41e862860.camel@sipsolutions.net> <875zingnzt.fsf@toke.dk> <14bbfcc8408500704c46701251546e7ff65c6fd0.camel@sipsolutions.net> <87r21bez5g.fsf@toke.dk> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.2 (3.34.2-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Wed, 2019-12-11 at 15:04 +0100, Toke Høiland-Jørgensen wrote: > Johannes Berg writes: > > > Btw, there's *another* issue. You said in the commit log: > > > > This patch does *not* include any mechanism to wake a throttled TXQ again, > > on the assumption that this will happen anyway as a side effect of whatever > > freed the skb (most commonly a TX completion). > > > > Thinking about this some more, I'm not convinced that this assumption > > holds. You could have been stopped due to the global limit, and now you > > wake some queue but the TXQ is empty - now you should reschedule some > > *other* TXQ since the global limit had kicked in, not the per-TXQ limit, > > and prevented dequeuing, no? > > Well if you hit the global limit that means you have 24ms worth of data > queued in the hardware; those should be completed in turn, and enable > more to be dequeued, no? Yes, but on which queues? Say you have some queues - some (Q1-Qn) got a LOT of traffic, and another (Q0) just has some interactive traffic. You could then end up in a situation where you have 24ms queued up on Q1-Qn (with n high enough to not have hit the per-queue AQL limit), right? Say also the last frame on Q0 was dequeued by the hardware, but the tx_dequeue() got NULL because of the AQL limit having been eaten up by all the packets on Q1-Qn. Now you'll no longer get a new dequeue attempt on Q0 (it was already empty last time, so no hardware reclaim to trigger new dequeues), and a new dequeue on the *other* queues will not do anything for this queue. johannes