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Date:      Tue, 28 Jun 2016 12:06:19 +0200
From:      Julien Charbon <jch@freebsd.org>
To:        freebsd-net@freebsd.org
Cc:        k simon <chio1990@gmail.com>, hiren panchasara <hiren@strugglingcoder.info>
Subject:   Re: TCP stack lock contention with short-lived connections
Message-ID:  <5635309e-3235-e574-9bd2-a7a484ac0825@freebsd.org>
In-Reply-To: <5665A78E.3090401@freebsd.org>
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> <53861209.2000306@verisign.com> <53880525.6000203@gmail.com> <5665A78E.3090401@freebsd.org>

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Content-Type: multipart/mixed; boundary="sLjvpJBQN2Eh2Alkrg63LMpUhdDa7ei1a"
From: Julien Charbon <jch@freebsd.org>
To: freebsd-net@freebsd.org
Cc: k simon <chio1990@gmail.com>,
 hiren panchasara <hiren@strugglingcoder.info>
Message-ID: <5635309e-3235-e574-9bd2-a7a484ac0825@freebsd.org>
Subject: Re: TCP stack lock contention with short-lived connections
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> <53861209.2000306@verisign.com>
 <53880525.6000203@gmail.com> <5665A78E.3090401@freebsd.org>
In-Reply-To: <5665A78E.3090401@freebsd.org>

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 Hi -net,

On 12/7/15 4:36 PM, Julien Charbon wrote:
> On 30/05/14 06:12, k simon wrote:
>>   Does any plan commit and MFC to the 10-stable ?
>=20
>  I got a bit of interest of having the performance improvements for
> short-lived TCP connections in 10-stable.  Just to share the current
> status to a wider audience:
>=20
>  - I maintain a stack of our TCP performance related patches for
> 10.2-RELENG here:
>=20
> https://github.com/verisign/freebsd/commits/10.2/tcp-scale

 Got more request to MFC TCP stack short-lived connection changes (see
below) in 10:

#1 Decrease lock contention within the TCP accept case by removing
the INP_INFO lock from tcp_usr_accept
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D271119

#2 In tcp_input(), don't acquire the pcbinfo global write lock for SYN
packets targeting a listening socket.
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D271119

#3 A connection in TIME_WAIT state before calling close() actually did
not received any RST packet.
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D273014

#4 Decompose TCP INP_INFO lock to increase short-lived TCP connections
scalability
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D286227

   Fix a kernel assertion issue introduced with r286227
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D286443

#5 Make clear that TIME_WAIT timeout expiration is managed solely by
tcp_tw_2msl_scan()
https://svnweb.freebsd.org/base?view=3Drevision&revision=3D286873

 If nobody complains, I plan to MFC them in stable/10.  After actually
quite a bunch of tests as I see a lot of changes that might impact these
MFCs (like TFO support, etc.).

--
Julien


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