Re: [Bloat] ADSL, ATM drivers, bloat, education & confusion

[Kevin Darbyshire-Bryant]

On 06/06/15 15:29, Sebastian Moeller wrote:

1) ATM interface 'backpressure' - is this Byte Queue Limits? (ifxmips_atm)
        Is there actual backpreassure from your ATM diver at all? As rar as I 
know france’s free had their boxes ATM driver modified to keep buffering low, 
and I believe David Woodhouse dd some work on another driver/the generic ATM 
layer, but I am not sure that any ATM driver actually defaults to sane 
buffering and sane back pressure.

That was my sort of point. On 'planet Kevin' (don't go there) the ATM driver would *know* the link is busy, or how many bytes it still had to shove over it and could offer some clue back up the stack to not bloat. I thought that's what BQL was supposed to do. Or another way of viewing: If ethernet interfaces ideally implement BQL why shouldn't ATM?

        How this is supposed to work? In an ideal work the CPE and the DSLAM 
would not over-buffer and www would not have to dedicate grey matter to work 
around their sort-commings ;) But as far as I can tell DSL sync rates for many 
lines are stable over weeks to months, so setting the shaper rarely is 
sufficient. Like when you notice that latency under load got worse…

Well again on 'planet Kevin' the CPE is OpenWrt. Apparenly it's under my control but I'm fighting my own lack of abilities, trying to sprint a marathon before I can even crawl. Looking at kernel sources when I can barely get 'hello world' to compile & run is asking for trouble :-) About a day ago I didn't know what an SKB was. https://www.coverfire.com/articles/queueing-in-the-linux-network-stack/ has been a revelation.

Best Regards
        Sebastian

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