Re: [PATCH v2] test: Update the threshold value for some perf tests

[Stefano Brivio <sbrivio@redhat.com>]

On Mon, 13 Oct 2025 15:39:32 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Mon, Oct 13, 2025 at 09:31:41AM +0800, Yumei Huang wrote:
> > The values are adjusted to better match results observerd on the
> > test hardware with 56-core Xeon Gold 6330 CPU and 126 GB RAM.  
> 
> Interesting.  That CPU is older than the one on my laptop (i7-12800H),
> which comfortably hit the old thresholds, but by less than a year (Q2
> 2021 versus Q1 2022).  At the same time it's a much fancier model for
> its generation.  I thought the Xeons might have been built with better
> memory bandwidth which probably has more effect on passt than the
> CPU's computational speed.
> 
> I'm not certain what machine Stefano was using to estimate the
> existing thresholds, but I'm guessing it was passt.top which is an AMD
> Ryzen 5 3600 - older than both of the above (2019).

Yep.

> passt is single threaded so the Xeon's many cores wouldn't help it,
> but it's still surprising that it can't keep up with the other
> machines we've tried on.

Kernels and LSMs might make a huge difference as well. I expect a
substantial system call overhead (because that's what it is here,
I guess?) might come from SELinux hooks.

Not that it really matters, I think, as long as numbers are reasonable
(and we don't make them worse with some unsuspecting change) I don't see
an actual problem with it.

-- 
Stefano