From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-f49.google.com (mail-lf1-f49.google.com [209.85.167.49]) (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 AC6F93B29E for ; Sat, 13 Apr 2019 03:11:31 -0400 (EDT) Received: by mail-lf1-f49.google.com with SMTP id k18so267611lfj.13 for ; Sat, 13 Apr 2019 00:11:31 -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; bh=TH4bRi7i4AdasmB+RPfDosQj6Z8WpfRDFj5iRocEvQ4=; b=df3pglJnajL8hZsvDTGV7cRjbGo10u2+HldRye1c2vOyqdjmMhtxXI8BRzpa63HYkY ukJLcnbbWL2KYo2dyey5nfLO3HUiZZ8r1lFd30VZtppZm4E7YTeptKgeSahJvlpwWPXe f4gJOWwXdzoQAkcjukJ1ThBO6MS/zLAqDfeFkgVPx0x/OOOtvaK7y4hMy0jqHSCvCjDC RM0udqJLxldJhgXcPUBg/7HgHumic+9hrMUYIuGp6fNyObE504ryJHJfAHdgQqi6cm8I COQQasYP9YWjrNz7Q8qTBqXOK0Pp0aiV3pLrpOdVrv9z8s9TtmUOGq6QrzRuxV9ZSUh+ LN1g== X-Gm-Message-State: APjAAAWeu7rSbdIaNhwivPGcet3O1eCgFpF0yMSdRsSDvSKpjsS/Y2+y rFahXiyf2YKaSlCpmF2vpqgQ6Q== X-Google-Smtp-Source: APXvYqzlR5nlz9XsWLLgYJFPEZn+8tQkUNRcHFcIZ1KhGWvPqF0lnyNjkrf2Ys80vx1rsYss5kqumA== X-Received: by 2002:a19:cc52:: with SMTP id c79mr7547897lfg.30.1555139490401; Sat, 13 Apr 2019 00:11:30 -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 p25sm2894465lfh.0.2019.04.13.00.11.28 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 13 Apr 2019 00:11:29 -0700 (PDT) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id E632C1800E9; Sat, 13 Apr 2019 08:45:06 +0200 (CEST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Joshua Zhao Cc: make-wifi-fast@lists.bufferbloat.net In-Reply-To: References: <878swfshsk.fsf@toke.dk> <87ftqnvvxl.fsf@toke.dk> X-Clacks-Overhead: GNU Terry Pratchett Date: Sat, 13 Apr 2019 08:45:06 +0200 Message-ID: <87d0lqwgi5.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Make-wifi-fast] tx queue stuck for many minutes 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, 13 Apr 2019 07:11:31 -0000 Joshua Zhao writes: > That makes sense. I guess missing TX completion could be potential suspect > and I'll check on that. > > On the other hand, why I ask about back-pressure is because when the > problem happens the UDP TX socket shows as stuck and doesn't take any new > packets. > > ~# netstat -tulnp > > Active Internet connections (only servers) > > Proto Recv-Q Send-Q Local Address Foreign Address State > PID/Program name > > udp 0 22400 0.0.0.0:48439 0.0.0.0:* > 2407/audiod-xxxxx > > Basically the "Send-Q" number stays as a very high number for long time (I > didn't save what the exact number is when the problem happens) in the above > example, so that the sendto() function simply fails. > This is why I wondered about back-pressure being applied. Otherwise > shouldn't UDP socket keeps sending and packets would be dropped by the > queue scheduler? I would expect so; mac80211 only ever returns NETDEV_TX_OK from its netif_start_xmit() function. Guess the socket layer can stall out for some reason, or something? -Toke