linux-kernel - Re: Packet timestamps (was: Re: Network performance degradation from 2.6.11.12 to 2.6.16.20)

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Message-Id: <200703061616.24959.dada1@cosmosbay.com>
Date:	Tue, 6 Mar 2007 16:16:24 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	"Vladimir B. Savkin" <master@...torb.msk.ru>
Cc:	netdev@...r.kernel.org, Andi Kleen <ak@...e.de>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	David Miller <davem@...emloft.net>, hawk@...u.dk,
	harry@...os.washington.edu, linux-kernel@...r.kernel.org,
	Rick Jones <rick.jones2@...com>
Subject: Re: Packet timestamps (was: Re: Network performance degradation from 2.6.11.12 to 2.6.16.20)

On Tuesday 06 March 2007 15:43, Vladimir B. Savkin wrote:
> On Tue, Mar 06, 2007 at 03:38:44PM +0100, Eric Dumazet wrote:
> > 2) "accurate_timestamps" is misleading.
> > 	Should be "disable_timestamps"
>
> Not, if default is 1, as in my patch.

Yes I saw this. I should write more words next time :)

Full explanation:
----------------------

If your tunable is named "accurate_timestamps" then a 0 value would mean :

Use a low precision timestamp (based on xtime for example) instead of a full 
resolution...

This is not what your patch does (while it could do that, but beware that 
net-2.6.22 includes now a ktime_t timestamping)

So :
------

It would be better to name the tunable "disable_timestamps", default 0 of 
course.... 
It would better describe what your patch is actually doing : Even if a tcpdump 
is running (so asking for timestamps), it wont have them because the sysctl 
disabled them.

Thank you

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