From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sujith Manoharan Subject: TCP performance regression Date: Mon, 11 Nov 2013 11:00:21 +0530 Message-ID: <21120.27501.32323.332316@gargle.gargle.HOWL> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from s72.web-hosting.com ([198.187.29.21]:57078 "EHLO s72.web-hosting.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900Ab3KKFeq (ORCPT ); Mon, 11 Nov 2013 00:34:46 -0500 Sender: netdev-owner@vger.kernel.org List-ID: Hi, The commit, "tcp: TSQ can use a dynamic limit" causes a large performance drop in TCP transmission with the wireless driver ath9k. With a 2-stream card (AR9462), the usual throughput is around 195 Mbps. But, with this commit, it drops to ~125 Mbps, occasionally reaching 130. If the commit is reverted, performance is normal again and I can get 190+ Mbps. Apparently, ath10k is also affected and a 250 Mbps drop is seen (from an original 740 Mbps). I am using Linville's wireless-testing tree. >>From the test machine: root@linux-test ~# uname -a Linux linux-test 3.12.0-wl-nodebug #104 SMP PREEMPT Mon Nov 11 10:27:56 IST 2013 x86_64 GNU/Linux root@linux-test ~# tc -d -s qdisc show dev wlan0 qdisc mq 0: root Sent 342682272 bytes 226366 pkt (dropped 0, overlimits 0 requeues 0) backlog 0b 0p requeues 0 root@linux-test ~# zgrep -i net_sch /proc/config.gz CONFIG_NET_SCHED=y CONFIG_NET_SCH_CBQ=m CONFIG_NET_SCH_HTB=m CONFIG_NET_SCH_HFSC=m CONFIG_NET_SCH_ATM=m CONFIG_NET_SCH_PRIO=m CONFIG_NET_SCH_MULTIQ=m CONFIG_NET_SCH_RED=m CONFIG_NET_SCH_SFB=m CONFIG_NET_SCH_SFQ=m CONFIG_NET_SCH_TEQL=m CONFIG_NET_SCH_TBF=m CONFIG_NET_SCH_GRED=m CONFIG_NET_SCH_DSMARK=m CONFIG_NET_SCH_NETEM=m CONFIG_NET_SCH_DRR=m CONFIG_NET_SCH_MQPRIO=m CONFIG_NET_SCH_CHOKE=m CONFIG_NET_SCH_QFQ=m CONFIG_NET_SCH_CODEL=m CONFIG_NET_SCH_FQ_CODEL=m CONFIG_NET_SCH_FQ=m CONFIG_NET_SCH_INGRESS=m # CONFIG_NET_SCH_PLUG is not set CONFIG_NET_SCH_FIFO=y If more information is required, please let me know. Sujith