From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [PATCH net-next] qdisc: validate skb without holding lock Date: Mon, 6 Oct 2014 16:12:35 +0200 Message-ID: <20141006161235.010033f5@redhat.com> References: <20141003.145647.1980640682969765484.davem@davemloft.net> <1412373477.17245.5.camel@edumazet-glaptop2.roam.corp.google.com> <1412375467.17245.16.camel@edumazet-glaptop2.roam.corp.google.com> <20141003.153645.72976986956341944.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: eric.dumazet@gmail.com, netdev@vger.kernel.org, therbert@google.com, hannes@stressinduktion.org, fw@strlen.de, dborkman@redhat.com, jhs@mojatatu.com, alexander.duyck@gmail.com, john.r.fastabend@intel.com, dave.taht@gmail.com, toke@toke.dk, brouer@redhat.com To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:2417 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752680AbaJFOND (ORCPT ); Mon, 6 Oct 2014 10:13:03 -0400 In-Reply-To: <20141003.153645.72976986956341944.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, 03 Oct 2014 15:36:45 -0700 (PDT) David Miller wrote: > From: Eric Dumazet > Date: Fri, 03 Oct 2014 15:31:07 -0700 > > > From: Eric Dumazet > > > > Validation of skb can be pretty expensive : > > > > GSO segmentation and/or checksum computations. > > > > We can do this without holding qdisc lock, so that other cpus > > can queue additional packets. > > [...] > > > > Turning TSO on or off had no effect on throughput, only few more cpu > > cycles. Lock contention on qdisc lock disappeared. This is good work! Lock contention significantly reduced! My 10G tests just 2x 10G netperf TCP_STREAM shows: With GSO=off TSO=off, _raw_spin_lock is now only at perf top#13 with 1.44% (80% from qdisc calls, 60% is from __dev_queue_xmit and 20% from sch_direct_xmit) (before with qdisc bulking is was 2.66%). The "show off" case is GSO=on TSO=off, where raw_spin_lock is now only at perf top#26 with 0.85% and only 54.74% comes from qdisc calls (52.07% sch_direct_xmit and 2.67% __dev_queue_xmit). This is some significant improvements to the kernels xmit layer, me very happy!!! :-))) Thanks everyone! -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer