netdev - Re: [PATCH v15 0/7] io_uring: add napi busy polling support

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Date: Wed, 31 Jan 2024 12:59:39 -0500
From: Olivier Langlois <olivier@...llion01.com>
To: Jens Axboe <axboe@...nel.dk>, Stefan Roesch <shr@...kernel.io>, 
	io-uring@...r.kernel.org, kernel-team@...com
Cc: ammarfaizi2@...weeb.org, netdev@...r.kernel.org, kuba@...nel.org
Subject: Re: [PATCH v15 0/7] io_uring: add napi busy polling support

On Wed, 2024-01-31 at 10:32 -0700, Jens Axboe wrote:
> 
> Thanks for testing!
> 
> Any chance that you could run some tests with and without NAPI that
> help
> validate that it actually works? That part is what I'm most
> interested
> in, not too worried about the stability of it as I have scrutinized
> it
> pretty close already.
> 

There is maybe a test that I can perform. The data that I receive is
timestamped. I have a small test program that checks the age of the
updates on their reception...

I would expect that it should be possible to perceive the busy polling
effect by comparing the average update age with and without the feature
enabled...

A word of warning... The service that my client is connecting to has
relocated recently. I used to have an RTT of about 8mSec with it to
about 400-500 mSec today...

because of the huge RTT, I am unsure that the test is going to be
conclusive at all...

However, I am also in the process of relocating my client closer to the
service. If you can wait a week or so, I should able to do that test
with a RTT < 1 mSec...

Beside that, I could redo the same test that Stefan did with the ping
client/server setup but would that test add any value to the current
collective knowledge?

I'll do the update age test when I restart my client and I'll report
back the result but my expectations aren't very high that it is going
to be conclusive due to the huge RTT.