From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [RFC] net: remove busylock Date: Thu, 19 May 2016 10:08:36 -0700 Message-ID: <1463677716.18194.203.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Alexander Duyck To: netdev Return-path: Received: from mail-pf0-f195.google.com ([209.85.192.195]:34932 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754514AbcESRIj (ORCPT ); Thu, 19 May 2016 13:08:39 -0400 Received: by mail-pf0-f195.google.com with SMTP id b66so8698599pfb.2 for ; Thu, 19 May 2016 10:08:39 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: busylock was added at the time we had expensive ticket spinlocks (commit 79640a4ca6955e3ebdb7038508fa7a0cd7fa5527 ("net: add additional lock to qdisc to increase throughput") Now kernel spinlocks are MCS, this busylock things is no longer relevant. It is slowing down things a bit. With HTB qdisc, here are the numbers for 200 concurrent TCP_RR, on a host with 48 hyperthreads. lpaa5:~# sar -n DEV 4 4 |grep eth0 10:05:44 eth0 798951.25 798951.75 52276.22 52275.26 0.00 0.00 0.50 10:05:48 eth0 798576.00 798572.75 52251.24 52250.39 0.00 0.00 0.75 10:05:52 eth0 798746.00 798748.75 52262.89 52262.13 0.00 0.00 0.50 10:05:56 eth0 798303.25 798291.50 52235.22 52233.10 0.00 0.00 0.50 Average: eth0 798644.12 798641.19 52256.39 52255.22 0.00 0.00 0.56 Disabling busylock (by using a local sysctl) lpaa5:~# sar -n DEV 4 4 |grep eth0 10:05:14 eth0 864085.75 864091.50 56538.09 56537.46 0.00 0.00 0.50 10:05:18 eth0 864734.75 864729.25 56580.35 56579.05 0.00 0.00 0.75 10:05:22 eth0 864366.00 864361.50 56556.74 56555.00 0.00 0.00 0.50 10:05:26 eth0 864246.50 864248.75 56549.19 56547.65 0.00 0.00 0.50 Average: eth0 864358.25 864357.75 56556.09 56554.79 0.00 0.00 0.56 That would be a 8 % increase.