Date: Wed, 28 May 2014 18:42:49 +0200 From: Julien Charbon <jcharbon@verisign.com> To: freebsd-net@freebsd.org Subject: Re: TCP stack lock contention with short-lived connections Message-ID: <53861209.2000306@verisign.com> In-Reply-To: <537FB51D.2060401@verisign.com> References: <op.w51mxed6ak5tgc@fri2jcharbon-m1.local> <op.w56mamc0ak5tgc@dul1rjacobso-l3.vcorp.ad.vrsn.com> <len481$sfv$2@ger.gmane.org> <537F39DF.1090900@verisign.com> <537FB51D.2060401@verisign.com>
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Hi, On 23/05/14 22:52, Julien Charbon wrote: > On 23/05/14 14:06, Julien Charbon wrote: >> On 27/02/14 11:32, Julien Charbon wrote: >>> On 07/11/13 14:55, Julien Charbon wrote: >>>> On Mon, 04 Nov 2013 22:21:04 +0100, Julien Charbon >>>> <jcharbon@verisign.com> wrote: >>>>> I have put technical and how-to-repeat details in below PR: >>>>> >>>>> kern/183659: TCP stack lock contention with short-lived connections >>>>> http://www.freebsd.org/cgi/query-pr.cgi?pr=183659 >>>>> >>>>> We are currently working on this performance improvement effort; it >>>>> will impact only the TCP locking strategy not the TCP stack logic >>>>> itself. We will share on freebsd-net the patches we made for >>>>> reviewing and improvement propositions; anyway this change might also >>>>> require enough eyeballs to avoid tricky race conditions introduction >>>>> in TCP stack. > > Joined the two cumulative patches (tcp-scale-inp-list-v1.patch and > tcp-scale-pcbinfo-rlock-v1.patch) we discussed the most at BSDCan 2014. At BSDCan 2014 we were also asked to provide flame graph [1][2] to highlight impacts of these TCP changes. The Dtrace sampling was done on a NIC receive queue IRQ bound core. o First CPU flame graph on 10.0-RELENG at 40k TCP connection/secs: https://googledrive.com/host/0BwwgoN552srvQi1JWG42TklfQ28/releng10-40k.html Note: - __rw_wlock_hard on ipi_lock contention is clear as usual. o Second, same test with all our patches applied (thus from 10.0-next branch [3]): https://googledrive.com/host/0BwwgoN552srvQi1JWG42TklfQ28/tcp-scale-40k.html Note: - Almost all __rw_wlock_hard on ipi_lock contention is converted in idle time. o Third, still using 10.0-next branch, the flame graph when doubling the rate to 80k TCP connection/sec: https://googledrive.com/host/0BwwgoN552srvQi1JWG42TklfQ28/tcp-scale-80k.html My 2 cents. [1] http://www.brendangregg.com/FlameGraphs/cpuflamegraphs.html [2] https://wiki.freebsd.org/201405DevSummit/NetworkStack [3] https://github.com/verisign/freebsd/commits/share/10.0-next -- Julien
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