Date: Sun, 24 Sep 2017 10:50:29 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Stephen Hurd <shurd@sasktel.net>, "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> Cc: Stephen Hurd <shurd@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r323942 - head/sys/net Message-ID: <3601ee57-2bf5-036a-a3d1-a4795847d0ec@selasky.org> In-Reply-To: <89d68ff8-84ed-83a6-4e77-9a321babe2fe@sasktel.net> References: <201709230135.v8N1ZE6S063264@repo.freebsd.org> <B28D9879-4ECF-43E4-9A58-51F616CEC4BE@lists.zabbadoz.net> <283397c7-a01e-3776-7ed3-b64d68003d0b@sasktel.net> <6F5DC92C-2CF6-4A33-9663-BFECB7DB65F2@lists.zabbadoz.net> <89d68ff8-84ed-83a6-4e77-9a321babe2fe@sasktel.net>
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On 09/24/17 01:46, Stephen Hurd wrote: > Bjoern A. Zeeb wrote: >> On 23 Sep 2017, at 6:32, Stephen Hurd wrote: >> >>> Bjoern A. Zeeb wrote: >>>> On 23 Sep 2017, at 1:35, Stephen Hurd wrote: >>>> >>>>> Author: shurd >>>>> Date: Sat Sep 23 01:35:14 2017 >>>>> New Revision: 323942 >>>>> URL: https://svnweb.freebsd.org/changeset/base/323942 >>>>> >>>>> Log: >>>>> Chain mbufs before passing to if_input() >>>>> >>>>> Build a list of mbufs to pass to if_input() after LRO. Results in >>>>> 12% small packet forwarding rate improvement. >>>> forwarding seems a confusing word here.. >>> >>> The test was small (64 byte frames) received on one interface, then >>> sent out on a different one using the net.inet.ip.forwarding sysctl >>> (controlled via the gateway_enable setting in rc.conf). >> >> Then this makes no sense as we don’t do LRO if forwarding is enabled >> on the machine; >> https://svnweb.freebsd.org/base/head/sys/netinet/tcp_lro.c?annotate=317390#l645 >> > > Basically, it changed from this: > > foreach (mbuf in rx) { > if (lro && tcp_lro_rx(mbuf) == 0) > continue; > if_input(mbuf) > } > > To this: > > prev_mbuf = first_mbuf = NULL; > foreach (mbuf in rx) { > if (lro && tcp_lro_rx(mbuf) == 0) > continue; > if (prev_mbuf) { > prev_mbuf->m_nextpkt = mbuf; > prev_mbuf = mbuf; > } > else { > first_mbuf = prev_mbuf = mbuf; > } > } > > if (first_mbuf) > if_input(first_mbuf); > > So while before it called if_input() for each separate mbuf that was not > LROed, it now builds a chain of mbufs that were not LROed, and makes a > single call to if_input() with the whole chain. For cases like packet > forwarding where no packets are LROed, performance is better. > Can such a similar logic be applied inside TCP LRO aswell? --HPS
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