Re: [9fans] env walk

[Peter Schay <pschay@pobox.com>]

As far as I can tell, the loop I proposed in envwalk() is a
linear search to walk to an environment variable.

The devwalk+envgen algorithm is n squared because the loop in envgen
is nested within the loop in devwalk.  It's amazing how that tiny
little loop in envgen can eat up time!

Pete


presotto@plan9.bell-labs.com wrote:
> 
> All the devices that use devwalk have n squared behavior.  It wasn't
> supposed to be a problem because n isn't supposed to be large for them.
> I agree that it's short sighted for something with potentially many files
> like #e.  Your solution is also O(n**2), though the constant
> is much smaller (no devdir inside the loop).  I'll replace the devwalk
> with your search and put it on the next update wrap.
> 
> Also, on network performance, we played a bunch with TCP speed after
> Dong Lin showed us how slow we were.  Last we tested our TCP stack,
> we came out somewhere between Linux and FreeBSD in speed between 2
> 500 MHZ Pentiums on a 100meg ether.  That's partially why loopbackmedium
> appeared, to see how much was stack and how much driver.  I'll run
> a new set of tests in a few weeks and post when I'm done.
> Since both all 3 OS's are moving targets, the validity
> of the tests is transient.  Sic transit perfunctio.