From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f68.google.com (mail-ed1-f68.google.com [209.85.208.68]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id B5C0C3CB36 for ; Thu, 4 Apr 2019 04:31:43 -0400 (EDT) Received: by mail-ed1-f68.google.com with SMTP id s39so1402213edb.2 for ; Thu, 04 Apr 2019 01:31:43 -0700 (PDT) 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:content-transfer-encoding; bh=Bsm1vVxwYVQoULCK7mCDz5ULCYHmGqc3KOmWINvNgm4=; b=W8NYlrLiPyLo1f8Kt/GpkoUjfqXnNSxMe8jj/xaxpjfn0rakWiOlvv0BoSbJk8t2Gc oZX9XaDYqAt5PvSC+Sb6QlfkBQ0+qAc25l6Big9DVsmbqVg8UvjDgneEsBbi+qO0LTta HQIzZ5DqfjjxAVhnS1pwlTykn1fLUf2/jw1ianu2FyDmcafuLXmRE7uuPLzNrwB0uBUh tAmZTj0+9lxRoZ5h/eRGvHDofEHuAkdqLMHMy8txw+BE819gwMHeVCg5+iOayWblwKN1 HGkmf8N5FToq4kSIRIO8iucrnUYrpLKmNul+eYplnaAO9RHXWxagZ4vm/ZQi6rioViZO jq0w== X-Gm-Message-State: APjAAAVjQAk5m+ddzqI+Q7XI9VtuI4LsX7iWM/HTJmmLqxGPgIs9GUwV ffUwjkdQxbuKWQGOvVZk763IjQ== X-Google-Smtp-Source: APXvYqy0nI3NvxiMR/YDaYwtd6uF7mlSwubfgtUL4T/La9x8We99+YViYodxB4hgJt7VjuBJB2WfBw== X-Received: by 2002:a50:bdc4:: with SMTP id z4mr2823292edh.199.1554366702830; Thu, 04 Apr 2019 01:31:42 -0700 (PDT) Received: from alrua-x1.borgediget.toke.dk (alrua-x1.vpn.toke.dk. [2a00:7660:6da:10::2]) by smtp.gmail.com with ESMTPSA id 25sm3418542ejv.27.2019.04.04.01.31.42 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 04 Apr 2019 01:31:42 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 921DA1804A5; Thu, 4 Apr 2019 10:31:41 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Yibo Zhao Cc: make-wifi-fast@lists.bufferbloat.net, linux-wireless@vger.kernel.org, Felix Fietkau , Rajkumar Manoharan , Kan Yan , linux-wireless-owner@vger.kernel.org In-Reply-To: <753b328855b85f960ceaf974194a7506@codeaurora.org> References: <20190215170512.31512-1-toke@redhat.com> <753b328855b85f960ceaf974194a7506@codeaurora.org> X-Clacks-Overhead: GNU Terry Pratchett Date: Thu, 04 Apr 2019 10:31:41 +0200 Message-ID: <87ftqy41ea.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Make-wifi-fast] [RFC/RFT] mac80211: Switch to a virtual time-based airtime scheduler 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: Thu, 04 Apr 2019 08:31:43 -0000 Yibo Zhao writes: > On 2019-02-16 01:05, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> This switches the airtime scheduler in mac80211 to use a virtual=20 >> time-based >> scheduler instead of the round-robin scheduler used before. This has a >> couple of advantages: >>=20 >> - No need to sync up the round-robin scheduler in firmware/hardware=20 >> with >> the round-robin airtime scheduler. >>=20 >> - If several stations are eligible for transmission we can schedule=20 >> both of >> them; no need to hard-block the scheduling rotation until the head of= =20 >> the >> queue has used up its quantum. >>=20 >> - The check of whether a station is eligible for transmission becomes >> simpler (in ieee80211_txq_may_transmit()). >>=20 >> The drawback is that scheduling becomes slightly more expensive, as we=20 >> need >> to maintain an rbtree of TXQs sorted by virtual time. This means that >> ieee80211_register_airtime() becomes O(logN) in the number of currently >> scheduled TXQs. However, hopefully this number rarely grows too big=20 >> (it's >> only TXQs currently backlogged, not all associated stations), so it >> shouldn't be too big of an issue. >>=20 >> @@ -1831,18 +1830,32 @@ void ieee80211_sta_register_airtime(struct >> ieee80211_sta *pubsta, u8 tid, >> { >> struct sta_info *sta =3D container_of(pubsta, struct sta_info, sta); >> struct ieee80211_local *local =3D sta->sdata->local; >> + struct ieee80211_txq *txq =3D sta->sta.txq[tid]; >> u8 ac =3D ieee80211_ac_from_tid(tid); >> - u32 airtime =3D 0; >> + u64 airtime =3D 0, weight_sum; >> + >> + if (!txq) >> + return; >>=20 >> if (sta->local->airtime_flags & AIRTIME_USE_TX) >> airtime +=3D tx_airtime; >> if (sta->local->airtime_flags & AIRTIME_USE_RX) >> airtime +=3D rx_airtime; >>=20 >> + /* Weights scale so the unit weight is 256 */ >> + airtime <<=3D 8; >> + >> spin_lock_bh(&local->active_txq_lock[ac]); >> + >> sta->airtime[ac].tx_airtime +=3D tx_airtime; >> sta->airtime[ac].rx_airtime +=3D rx_airtime; >> - sta->airtime[ac].deficit -=3D airtime; >> + >> + weight_sum =3D local->airtime_weight_sum[ac] ?: sta->airtime_weight; >> + >> + local->airtime_v_t[ac] +=3D airtime / weight_sum; > Hi Toke, > > Please ignore the previous two broken emails regarding this new proposal= =20 > from me. > > It looks like local->airtime_v_t acts like a Tx criteria. Only the=20 > stations with less airtime than that are valid for Tx. That means there=20 > are situations, like 50 clients, that some of the stations can be used=20 > to Tx when putting next_txq in the loop. Am I right? I'm not sure what you mean here. Are you referring to the case where new stations appear with a very low (zero) airtime_v_t? That is handled when the station is enqueued. >> + sta->airtime[ac].v_t +=3D airtime / sta->airtime_weight; > Another question. Any plan for taking v_t overflow situation into=20 > consideration? u64 might be enough for low throughput products but not=20 > sure for high end products. Something like below for reference: The unit for the variable is time, not bytes, so it is unaffected by throughput. 2**64 microseconds is 584554 *years* according to my 'units' binary, so don't think we have to worry too much about this overflowing ;) -Toke