Re: [PATCH linux-next] net: record times of netdev_budget exhausted

yang.yang29
2022-12-06T02:35:30Z

On Tue, 6 Dec 2022 09:53:05 +0800 (CST) kuba@kernel.org wrote:
> time_squeeze is extremely noisy and annoyingly useless,
> we need to understand exactly what you're doing before
> we accept any changes to this core piece of code.

The author of "Replace 2 jiffies with sysctl netdev_budget_usecs
to enable softirq tuning" is Matthew Whitehead, he said this in
git log: Constants used for tuning are generally a bad idea, especially
as hardware changes over time...For example, a very fast machine
might tune this to 1000 microseconds, while my regression testing
486DX-25 needs it to be 4000 microseconds on a nearly idle network
to prevent time_squeeze from being incremented.

And on my systems there are huge packets on the intranet, and we
came accross with lots of time_squeeze. The idea is that, netdev_budget*
are selections between throughput and real-time. If we care throughput
and not care real-time so much, we may want bigger netdev_budget*.

In this scenario, we want to tune netdev_budget* and see their effect
separately.

By the way, if netdev_budget* are useless, should they be deleted?

Thanks.