From: Ben Hutchings <bhutchings@solarflare.com>
To: raj ravi <mekaviraj@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: GSO / TSO offload dependency
Date: Sun, 28 Feb 2010 19:30:46 +0000 [thread overview]
Message-ID: <1267385446.2282.119.camel@localhost> (raw)
In-Reply-To: <de0a9dcb1002280900k728b241fyd72112defc0336ea@mail.gmail.com>
On Sun, 2010-02-28 at 22:30 +0530, raj ravi wrote:
> Hi,
> I m currently working on TSO feature in Linux network driver.
>
> Please correct my understanding.
>
> GSO - Generic segmentation offload - does not require any hardware support.
>
> TSO - TCP segmentation offload - does require hardward support
>
>
> Does TSO needs GSO to be turned on? OR in other words, can I have
> GSO disabled and TSO Enabled ?
> I beleive the code is tied between both offload...but not sure about
> the above possibility... please clarify.
Segmentation/fragmentation can be done in one of three places:
1. By the transport protocol, when constructing skbs to be queued
2. By the transport protocol, when an skb is about to be passed to the
device (enabled by NETIF_F_GSO)
3. By the device driver and hardware (enabled by NETIF_F_TSO,
NETIF_F_UFO, etc.)
Depending on the context, 'GSO' can refer either to case 2, or to both
cases 2 and 3. TSO does not need the NETIF_F_GSO feature to be turned
on, but in some contexts it is considered to be included in GSO.
> Just before handing over the packets to the Network driver,
> segmentation is carried out a call to dev_gso_segment ( ) function.
> Given GSO is enabled, It will take care about creating TCP and other
> protocol segments too, even if TSO is disabled.. ..correct ?
Correct.
> If hardware supports TSO, and If TSO and GSO are both enabled, ...
> what will happen to segmentation assembly by means of GSO ...
> GSO will not do any segmentatoin assembly for TCP alone and will do
> for other protocols ?? bit confused here? Please clarify.
Your understanding is correct.
Ben.
--
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
next prev parent reply other threads:[~2010-02-28 19:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-28 17:00 GSO / TSO offload dependency raj ravi
2010-02-28 19:30 ` Ben Hutchings [this message]
2013-06-05 9:28 ` Deepak
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