From: David Miller <davem@davemloft.net>
To: eric.dumazet@gmail.com
Cc: herbert@gondor.apana.org.au, thomas.jarosch@intra2net.com,
netdev@vger.kernel.org, edumazet@google.com,
steffen.klassert@secunet.com, bhutchings@solarflare.com
Subject: Re: tcp: Do not apply TSO segment limit to non-TSO packets
Date: Fri, 02 Jan 2015 15:36:55 -0500 (EST) [thread overview]
Message-ID: <20150102.153655.1853692198479011402.davem@davemloft.net> (raw)
In-Reply-To: <1420223040.32621.6.camel@edumazet-glaptop2.roam.corp.google.com>
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 02 Jan 2015 10:24:00 -0800
> On Thu, 2015-01-01 at 00:42 +1100, Herbert Xu wrote:
>> Firstly not many people test non-TSO code paths anymore so bugs
>> are likely to persist for a long time there. Perhaps it's time
>> to remove the non-TSO code path altogether? The GSO code path
>> should provide enough speed-up in terms of boosting the effective
>> MTU to offset the cost of copying.
>
>> Secondly why are we dealing with hardware TSO segment limits
>> by limiting the size of the TSO packet in the TCP stack? Surely
>> in this case GSO is free since there won't be any copying?
>
> It might depends on the device capabilities.
>
> Non TSO/GSO path is known to be better for devices unable to perform TX
> checksumming, as we compute the checksum at the time we copy data from
> user to kernel (csum_and_copy_from_user() from tcp_sendmsg())).
Non-SG capable devices suffer in this scenerio as well.
next prev parent reply other threads:[~2015-01-02 20:37 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-29 11:44 [bisected] xfrm: TCP connection initiating PMTU discovery stalls on v3.12+ Thomas Jarosch
2014-12-01 10:25 ` Herbert Xu
2014-12-01 11:20 ` Thomas Jarosch
2014-12-31 13:39 ` tcp: Do not apply TSO segment limit to non-TSO packets Herbert Xu
2014-12-31 13:42 ` Herbert Xu
2015-01-02 18:24 ` Eric Dumazet
2015-01-02 20:36 ` David Miller [this message]
2015-01-02 22:01 ` Herbert Xu
2015-01-02 22:06 ` David Miller
2015-01-02 22:09 ` Herbert Xu
2015-01-02 21:13 ` David Miller
2015-01-16 10:45 ` Thomas Jarosch
2015-01-16 10:50 ` Herbert Xu
2015-01-16 11:03 ` Thomas Jarosch
2015-01-19 13:39 ` Thomas Jarosch
[not found] ` <CANn89i+U-PFbuUrp08s3Ec8BmjPFq1zj8Aj2=vPVO4-iiLkTuw@mail.gmail.com>
2015-01-19 22:36 ` Herbert Xu
2015-01-19 22:38 ` Eric Dumazet
2015-01-19 22:40 ` Herbert Xu
2014-12-01 13:17 ` [bisected] xfrm: TCP connection initiating PMTU discovery stalls on v3.12+ Wolfgang Walter
2014-12-01 16:41 ` Wolfgang Walter
2014-12-05 12:09 ` Wolfgang Walter
2014-12-05 13:26 ` Eric Dumazet
2014-12-08 22:20 ` Wolfgang Walter
2014-12-09 8:54 ` Thomas Jarosch
2014-12-09 14:26 ` [bisected] xfrm: TCP connection initiating PMTU discovery stalls on v3 Eric Dumazet
2014-12-09 14:49 ` Thomas Jarosch
2014-12-09 20:36 ` Wolfgang Walter
2014-12-09 21:40 ` Eric Dumazet
2014-12-10 18:34 ` Wolfgang Walter
2014-12-10 19:10 ` Eric Dumazet
2014-12-11 0:36 ` Wolfgang Walter
2014-12-12 16:58 ` Wolfgang Walter
2014-12-12 17:27 ` Eric Dumazet
2014-12-12 20:31 ` Wolfgang Walter
2014-12-12 21:30 ` Thomas Jarosch
2014-12-12 22:31 ` Eric Dumazet
2014-12-12 23:47 ` Wolfgang Walter
2014-12-13 0:15 ` Eric Dumazet
2014-12-13 0:43 ` Wolfgang Walter
2014-12-15 18:04 ` Wolfgang Walter
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