Re: loaded router, excessive getnstimeofday in oprofile

[Andi Kleen]

On Wed, Aug 27, 2008 at 09:49:10AM -0700, Rick Jones wrote:
> Andi Kleen wrote:
> >>Those banks really want to crank down on latency - to the point they 
> >>start disabling interrupt coalescing.  I bet they'd toss anything out 
> >>they could to shave another microsecond.
> >
> >
> >This change would actually likely lower their latency.
> 
> I'm guessing you mean increase their latency?  I agree, it could - 
> depends entirely on the PPS in production I suspect.

No, moving the time stamps into the socket decreases latency
for all packets that don't need time stamps. And they likely 
have some packets which don't need time stamps too.

As a secondary effect if they use a RT kernel it might
be also beneficial to do the (depending on the platform)
costly time stamp in the lower priority socket context
than in the high priority interrupt thread.

-Andi

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