netdev - Re: txqueuelen has wrong units; should be time

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Date:	Sun, 27 Feb 2011 03:27:45 -0500
From:	Albert Cahalan <acahalan@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Mikael Abrahamsson <swmike@....pp.se>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: txqueuelen has wrong units; should be time

On Sun, Feb 27, 2011 at 2:54 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le dimanche 27 février 2011 à 08:02 +0100, Mikael Abrahamsson a écrit :
>> On Sun, 27 Feb 2011, Albert Cahalan wrote:
>>
>> > Nanoseconds seems fine; it's unlikely you'd ever want
>> > more than 4.2 seconds (32-bit unsigned) of queue.
...
> Problem is some machines have slow High Resolution timing services.
>
> _If_ we have a time limit, it will probably use the low resolution (aka
> jiffies), unless high resolution services are cheap.

As long as that is totally internal to the kernel and never
getting exposed by some API for setting the amount, sure.

> I was thinking not having an absolute hard limit, but an EWMA based one.

The whole point is to prevent stale packets, especially to prevent
them from messing with TCP, so I really don't think so. I suppose
you do get this to some extent via early drop.
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