TSO

[Scott Long]

Are you proposing that the network stack track the physical memory segment details of the mbufs as they are formed and chained together?

Scott

On Feb 26, 2014, at 10:27 AM, Jack Vogel <jfvogel at gmail.com> wrote:

> Drivers have to work with whatever the requirements/limitations of the
> hardware,
> if you have a 5 lb sack you shouldn't be surprised if some drops when you
> shove
> 6 lbs at it :)
> 
> Why not have this limit in the interface so the stack can avoid exceeding
> it?
> 
> Jack
> 
> 
> 
> 
> On Wed, Feb 26, 2014 at 10:07 AM, John-Mark Gurney <jmg at funkthat.com> wrote:
> 
>> Sami Halabi wrote this message on Wed, Feb 26, 2014 at 19:37 +0200:
>>> I'm reading (almost) all mailing emails in mailig list...
>>> 
>>> Almost every / many problem in network performancr / packets loss ended
>> up
>>> suggesting disabling TSO.
>>> 
>>> I wonder why.. Is it a bug in the implementation? Or bybdesign?
>>> What are the usecases that TSO is needed? Myabe  it should be disabled bt
>>> default?
>> 
>> It looks like most of the problems are in drivers that don't handle
>> packets with a large number of segments properly...  The problem is
>> that some drivers limit to how segments a packet can be broken into, and
>> then if they receive such a packet, instead of doing their darnest to
>> deliver it, they drop it...
>> 
>> There are some patches that help address the issue...
>> 
>> Drivers should complain more loudly when a packet gets dropped by the
>> driver, since it is likely that the OS may retry the same packet,
>> just to have it fail, though sometimes it'll try a different set, and
>> it might go through, so all the user may notice is a slight lag if
>> they notice anything at all...
>> 
>> --
>>  John-Mark Gurney                              Voice: +1 415 225 5579
>> 
>>     "All that I will do, has been done, All that I have, has not."
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