netdev - Re: [PATCH net-next] tcp: auto corking

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1386351976.30495.266.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 06 Dec 2013 09:46:16 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	David Laight <David.Laight@...LAB.COM>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] tcp: auto corking

On Fri, 2013-12-06 at 08:06 -0800, Rick Jones wrote:
> On 12/06/2013 02:30 AM, David Laight wrote:
> >> From: Eric Dumazet <edumazet@...gle.com>
> >>
> >> With the introduction of TCP Small Queues, TSO auto sizing, and TCP
> >> pacing, we can implement Automatic Corking in the kernel, to help
> >> applications doing small write()/sendmsg() to TCP sockets.
> >
> > Presumably this has the greatest effect on connections with Nagle
> > disabled?
> 
> I was wondering why Nagle didn't catch these things as well.  The 
> netperf command line Eric provided though didn't include the 
> test-specific -D option that would have disabled Nagle.  At least not 
> unless the "super_netperf" wrapper was adding it.
> 
> So, why doesn't Nagle catch what is presumably a sub-MSS send while 
> there is data outstanding on the connection?

super_netperf do not add any option.

Note the netperf results do no really show the improvements of this
patch. It's a side effect of the short cut.

You kind of need a TCP_RR workload, but splitting the request into small
chunks.

Well written applications use TCP_CORK or MSG_MORE, but unfortunately
many applications are not well written.

(Or people tried TCP_CORK in the past and got bitten by various bugs in
TCP stack that we fixed only last year)


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html