From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [207.211.31.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 355EC3B2A4 for ; Sat, 9 Nov 2019 06:22:56 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1573298575; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ygt9ehkmdDMxdmk4kMVpOxO+qyc90ZiyWuvotbEdwzQ=; b=cqZYORstCaNQAV5z+N3F3MCpgTHmMxprgEh2cnx2qXiQuzY7rviV2fYUMoyBE3dNAUkeXm RjGwjWKKawQgFi32Ic1/WjpYmZpPeufcQC1DTEDJTbdxTBxIjview2NX/FtjGGNic3tfyX yXHpqYJfOQjDrWpDmsfv4q69IWwYXzA= Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-163-AIYIyhTRPnGWMqIq9BM0lQ-1; Sat, 09 Nov 2019 06:22:52 -0500 Received: by mail-lj1-f197.google.com with SMTP id u6so1756570ljg.8 for ; Sat, 09 Nov 2019 03:22:52 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=LMrVkbjMH7hPzH5T4kkvtcS+8ogevDtCcANls+17jFo=; b=qlRwZRyTGl3jTTYiuQLYYWs8UJTcQ5BJusGZVUDFQH7qMrSumwFRNiWpLiPv+G2u4J /x8q1RMHQVsYuuNdtE8hgd+yejfd+OC2PGtZaWWZIriSociJwk2CD3QIDyhced20djP6 qfCbhzNjWyyCtdTiTtOWtWIa8rB5Z7ohNGwigr6vSDXny4K0MOU/rLR8TfRiHcmK8Hii unyobYzlnN1ma8TXSbAlXb7UHe21x0V1wmdP/d1X70N8yxZxSX+jJ/yLsOvO5zfhB3Yi xMM6fh872kjrBOijdt0ochUHCL66Lp8jX/AmQ5Tp1J4Y3YVzvWHT5I5LRWTXZHCRUIHq Slbw== X-Gm-Message-State: APjAAAVjtwKq3PibcSK77uDO1v4TEbmOQ1iFj+sXOv5pVranqvkb0lC+ 2q4Gto6Tvs6/TJA0JUGKRpM3Y+KBiWq7cH/I/JtgKQMcsE8f9ZZ7yJq83ur4prXIXN1vDlZTO5P Wpy9he5YBV9Y7XOEO8RuCDWWVcjVFduN++Sg= X-Received: by 2002:a19:ec16:: with SMTP id b22mr10517161lfa.74.1573298571133; Sat, 09 Nov 2019 03:22:51 -0800 (PST) X-Google-Smtp-Source: APXvYqz9Bw/mpsvE1bxpMagaaC8U31L/+lxFJA0jz6rY1xP5NdI110zv41vIFbwH9MLhnKK8I31y9g== X-Received: by 2002:a19:ec16:: with SMTP id b22mr10517148lfa.74.1573298570999; Sat, 09 Nov 2019 03:22:50 -0800 (PST) Received: from alrua-x1.borgediget.toke.dk ([2a00:7660:6da:443::2]) by smtp.gmail.com with ESMTPSA id r12sm6449887lfp.63.2019.11.09.03.22.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 09 Nov 2019 03:22:50 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 960BE1800CC; Sat, 9 Nov 2019 12:22:49 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Kan Yan , Johannes Berg Cc: linux-wireless@vger.kernel.org, Make-Wifi-fast , ath10k@lists.infradead.org, John Crispin , Lorenzo Bianconi , Felix Fietkau , Rajkumar Manoharan , Kevin Hayes In-Reply-To: References: <157182473951.150713.7978051149956899705.stgit@toke.dk> <157182474287.150713.12867638269538730397.stgit@toke.dk> <1a2eb096119c9029e67caf797564d6511c8803a7.camel@sipsolutions.net> <87a796fxgd.fsf@toke.dk> <874kzefwt3.fsf@toke.dk> <300bf0146db6c0d5890699b3911d35174d28c9c0.camel@sipsolutions.net> X-Clacks-Overhead: GNU Terry Pratchett Date: Sat, 09 Nov 2019 12:22:49 +0100 Message-ID: <87k189qoom.fsf@toke.dk> MIME-Version: 1.0 X-MC-Unique: AIYIyhTRPnGWMqIq9BM0lQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Subject: Re: [Make-wifi-fast] [PATCH v6 3/4] mac80211: Implement Airtime-based Queue Limit (AQL) X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 09 Nov 2019 11:22:56 -0000 Kan Yan writes: > It is most likely just insufficient locking. active_txq_lock is per > AC, can't protect local->aql_total_pending_airtime against racing > conditions: > void ieee80211_sta_update_pending_airtime(...) > { > spin_lock_bh(&local->active_txq_lock[ac]); > ... > local->aql_total_pending_airtime -=3D tx_airtime; > ... > spin_unlock_bh(&local->active_txq_lock[ac]); > } Ohh, right; didn't even realise those were not per-AC as well... > After changing it to atomic_t, no more aql_total_pending_airtime > underflow so far :). Using atomic operation should also help reduce > CPU overhead due to lock contention, as > ieee80211_sta_update_pending_airtime() is often called from the tx > completion routine triggered by interrupts, often in a different core > than where __ieee80211_schedule_txq() is running. > > I will post a new version a bit later if the test goes well. Awesome! :) -Toke