Re: [MirageOS-devel] towards a common Mirage 'FLOW' signature

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

On 20 Jun 2014, at 21:19, Dave Scott <Dave.Scott@xxxxxxxxxx> wrote:

>>> 
>>> and we could expose TCP buffers or the vchan ring size.  What use would 
>>> this information be to an application, though?
>> 
>> if i'm following this correctly, couldn't the application use this to do 
>> things like customise TCP congestion control behaviour by fiddling with the 
>> receive window? 
> 
> Maybe we should start by cataloging our current buffer management and see if 
> we can see any nice patterns? We have a nice set of protocols now.

The buffers all take different forms though -- unless the application 
specifically knows that it's a TCP flow, it can't take any sensible action 
based on predicted congestion behaviour.  And this would be entirely wrong 
behaviour if the buffer size it gets back is actually a (lossless) vchan ring 
buffer size instead.

So my point is that rather than exposing the buffer size as an integer, it 
would be worth figuring out some use cases for when applications would need to 
know the buffer size (as opposed to, for example, having a high level 
"sendfile"-style API that provides more declarative knowledge to the lower 
levels of the communications stack).

-anil
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