netdev - Re: [PATCH net-next] Replace constant with sysctl netdev_budget

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Message-ID: <1492441894.10587.105.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 17 Apr 2017 08:11:34 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Matthew Whitehead <tedheadster@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next] Replace constant with sysctl
 netdev_budget_jiffies to enable tuning

On Mon, 2017-04-17 at 10:29 -0400, Matthew Whitehead wrote:
> Constants used for tuning are generally a bad idea, especially as hardware
> changes over time. Replace the constant '2' with netdev_budget_jiffies to
> enable sysadmins to tune the behavior. Also document the variable.
> 
> For example, a very fast machine might tune this to 1, while my regression
> testing 486DX-25 needs it to be 4 on a nearly idle network to prevent
> time_squeeze from being incremented.

Hi Matthew

What is the problem with this 'time_squeeze' being incremented ?

This is an indicator, but not something bad per se.

Maybe your 486DX-25 should use HZ=100 ;)

Really I do not believe we should let admins/users play with this limit,
they will most likely shoot themselves.

Anyway, exporting in /proc/sys some time limit in 'jiffies' is not
recommended. We prefer portable msecs , usec or nanosec units.

Thanks.