[Make-wifi-fast] Flent test hardware

Pete Heist peteheist at gmail.com
Mon Nov 6 19:32:19 EST 2017

> On Nov 5, 2017, at 9:15 PM, Jonathan Morton <chromatix99 at gmail.com> wrote:
> Regarding single-core performance, the Sempron 3850 may be better in that respect than my E-450, which itself is perfectly capable of handling GigE at line rate (unlike an Atom).  It has an improved core design which may compensate for the lower clock speed.
> There are three members of AMD's "cat" family: Bobcat, Jaguar, Puma.  My E-450 has Bobcat, which is the oldest and maxes out at 1.65 GHz (there is no turbo clock).  Various consoles got Jaguar cores, as did the Kabini APU which forms your Sempron.  The Puma core is the newest, and appears in "Carrizo-L" APUs in last year's netbooks.  The design improvements between Bobcat and Jaguar are much larger than between Jaguar and Puma; consult Agner Fog's optimisation manuals if you want to know the gory details.
> The AM1 Kabini family also includes the Athlon 5150 and 5350, which are exactly the same as the 3850 except for clock speeds.  If the 3850 isn't fast enough, you can get an easy 50% boost from upgrading to the 5350.

These days it seems like most hardware is capable of GigE at line rate, but the smoothness of individual flows or other factors may be affected by CPU, either cores or speed. I wrote a script to run rrul_be_nflows over the loopback adapter and vary a few things:

- number of flows
- number of CPU cores enabled
- CPU frequency
- whether or not to limit loopback to 2gbit (simulating GigE)

This was an attempt to learn more about how the number of cores and CPU frequency can affect the results, but because I don’t actually have a box with two NICs and this uses loopback, it's just for learning, and should be taken with a grain of salt. Here are a few of the results from my MBP and Mini (six tabs of results):

https://docs.google.com/spreadsheets/d/1MVxGsreiGKNXhfkMIheNFrH_GVllFfiH9RU5ws5l_aY/edit#gid=739582898 <https://docs.google.com/spreadsheets/d/1MVxGsreiGKNXhfkMIheNFrH_GVllFfiH9RU5ws5l_aY/edit#gid=739582898>

Not too many surprises:
- I saw more dramatic differences overall when going from 1-2 cores (not good to test with only a single core)
- other things being equal, more cores are capable of higher throughput, but > 4 cores didn’t change much on my MBP
- with higher flow counts, more cores can make individual flows a bit smoother, and ping times sometimes lower and smoother
- I’d rather have a dual-core 1.6 GHz Core 2 Duo than a single-core 2.26 GHz Core 2 Duo, but because my hardware doesn’t let me lower CPU frequency to half of maximum, I couldn’t test a doubling of frequency vs going from 1-2 cores, which would be interesting to me (anyone else with hardware that can do that care to try?)

If anyone wants to run the script (takes a little modification), it’s here:

https://drive.google.com/file/d/1oasB3ePDMMr1WdRi_8koQmRO_qUjVB52/view?usp=sharing <https://drive.google.com/file/d/1oasB3ePDMMr1WdRi_8koQmRO_qUjVB52/view?usp=sharing>

As for the hardware, running everything on one box looks more complicated than I thought, not just because of Flent, but because of the scripts I wrote for setup and teardown and what they do. So now I’m thinking of taking one for the team and getting two boxes to avoid the hassle. I’ll still see.

Anyway, I added some ASUS / Intel builds for more on the high end:

https://docs.google.com/spreadsheets/d/1MVxGsreiGKNXhfkMIheNFrH_GVllFfiH9RU5ws5l_aY/edit#gid=199471438 <https://docs.google.com/spreadsheets/d/1MVxGsreiGKNXhfkMIheNFrH_GVllFfiH9RU5ws5l_aY/edit#gid=199471438>

If I ever see a comparison between the effects of doubling clock speed or going from 2-4 cores, it might help decide on the CPU.
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