bzero & bcopy alignment

[Marius Nuennerich]

On Sun, 21 Jan 2007 23:25:14 +0100
Ivan Voras <ivoras at fer.hr> wrote:

> Luigi Rizzo wrote:
> > On Sun, Jan 21, 2007 at 10:41:09PM +0100, Ivan Voras wrote:
> >> Following recent discussion on alignment of bzero() and bcopy(), I've
> >> added some statistics collecting code to bzero() and bcopy() for
> >> practice (on a RELENG_6 box), and here are the cumulative results for
> >> argument alignment:
> > 
> > i think these profiles depend heavily on the hardware
> > and usage patterns.
> 
> Yes, I agree. For what it's worth, this was on vmware, almost no network
> activity.
> 
> > e.g. some network drivers force you to aligned buffers
> > which results in misaligned payload requesting in
> > turn an unaligned bcopy. Not that one can help with this,
> > but i think that is also important to locate the locations
> > in the source where the poorly aligned (1-2, maybe
> > 4 and 8 to some degree) ops occur.
> 
> Any magic tricks to identify the caller of "current" function in the kernel?

I don't know if the dtrace port is ready for this, but afaik it would
be easy with dtrace.