[Cerowrt-devel] performance numbers from WRT1200AC (Re: Latest build test - new sqm-scripts seem to work; "cake overhead 40" didn't)
dave.taht at gmail.com
Fri Jun 26 12:34:28 EDT 2015
On Fri, Jun 26, 2015 at 9:18 AM, Jonathan Morton <chromatix99 at gmail.com> wrote:
> Hypothesis: this might have to do with the receive path. Some devices might
> have more capacity than others to buffer inbound packets until the CPU can
> get around to servicing them.
*Good* hypothesis. I am certain I have seen this on multiple occasions
on other hardware. Hard to confirm.
Wet paint... so I finally got off my arse and looked at the driver this morning.
given that this is a multi-core box, I would lean towards a smaller
napi_poll_weight, which unfortunately is a constant (64) in the code.
4 cores can take interrupts faster. (and I hate napi on routers) I
have sometimes longed for an IQL (ingress queue limits) to also handle
differences in packet size, dynamically changing the poll weight based
on load - increasing it for loads with lots of small packets,
decreasing it for lots of big packets.
Furthermore this thing is doing software gro (up to 64 packets at a
time) which is a LOT of processing at this layer in the stack.
Its a two line patch to cut the weight to 16, but I have never managed
to get a working build for this platform.
> - Jonathan Morton
> Cerowrt-devel mailing list
> Cerowrt-devel at lists.bufferbloat.net
worldwide bufferbloat report:
What will it take to vastly improve wifi for everyone?
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