Re: loaded router, excessive getnstimeofday in oprofile

Jarek Poplawski
2008-08-27T17:14:22Z

Stephen Hemminger wrote, On 08/27/2008 06:17 PM:

> On Wed, 27 Aug 2008 14:54:12 +0200
> Andi Kleen <andi@firstfloor.org> wrote:
>
>> Evgeniy Polyakov <johnpol@2ka.mipt.ru> writes:
>>> Yup, this innocent toys can end up with this such behaviour on modern
>>> highly loaded machines.
>> I and also other people had some patches to move the time stamp
>> measuring into the socket. This way the time stamping didn't need to
>> be enabled on all packets, only on those that actually end up at a
>> socket that requires the time stamp.
>>
>> Unfortunately DaveM didn't like it because some bank wanted
>> different semantics, see the discussion in
>> http://thread.gmane.org/gmane.linux.network/91679
>>
>> Perhaps you can find out which bank it was and send them a bill for
>> your CPU time ;-)
>>
>> -Andi
>>
>
> Look at /proc/net/ptype to see if any AF_PACKET sockets are open.
> There are several causes of this:
> * Applications like DHCP use AF_PACKET when they could use something else
> * AF_PACKET API was poorly designed and always has timestamps
> * The choice was made to get more accurate timestamps by stamping early in
> receive code. A better alternative would be to do it in protocol handler
> after the socket filter. Sorry, Andi socket layer is too late.
> * No driver is using hardware mechanisms to get accurate/free timestamps.
> I was working on sky2, but never was stable/complete.
>
> Easist advice now is to fix userspace.

And what is working advice?

Why exactly admin can't chose between 2 alternatives here?

Jarek P.