Re: [PATCH v3 00/10] tcp: Fix throughput issues with non-local peers

[Stefano Brivio <sbrivio@redhat.com>]

Hi Max,

On Mon, 08 Dec 2025 01:11:56 -0700
Max Chernoff <git@maxchernoff.ca> wrote:

> Hi Stefano,
> 
> On Mon, 2025-12-08 at 08:20 +0100, Stefano Brivio wrote:
> > With this series, I'm getting the expected (wirespeed) throughput for
> > transfers between peers with varying non-local RTTs: I checked
> > different guests bridged on the same machine (~500 us) and hosts with
> > increasing distance using iperf3, as well as HTTP transfers only for
> > some hosts I have control over (500 us and 5 ms case).
> >
> > With increasing RTTs, I can finally see the throughput converging to
> > the available bandwidth reasonably fast:  
> 
> Thanks for the patch, but this unfortunately seems to make things worse
> in my testing (with curl/https). Using my benchmarking script from the
> earlier thread, with a 10MB file size and a 30s timeout:

Thanks for re-testing. I actually wanted to get back to you about your
sysctl values, but, in general, I don't think things can work reliably
with the values you shared for tcp_notsent_lowat.

Does this (upload now taking longer/timing out with 50 ms RTT) also
happen without "custom" values for tcp_notsent_lowat?

I tested things quite extensively in that RTT region (without custom
sysctl values) and the improvement looks rather consistent to me.

-- 
Stefano