Re: Phase 2 takes too much time to complete

[Mark Wielaard <mjw at redhat dot com>]

Hi Roberto,

On Wed, 2009-02-11 at 11:31 -0500, Frank Ch. Eigler wrote:
> Roberto Natella <rnatella@gmail.com> writes:
> 
> > [...]  On my system (RHEL4 with 2.6.25 kernel; dual Intel Xeon(TM)
> > CPU 2.80GHz with HT; 5 GB RAM), phase 2 takes about half an hour to
> > complete. [...]
> 
> That's wacky!

30 minutes is indeed a little excessive.
I never seen anything take that long.
Do you have a sample stap invocation that shows this?
Are there any specifics about your kernel build that might be different
from others?

> Second, this code uses "endl" a lot, which can result in premature
> buffer flush syscalls.  If your strace is showing a lot of small
> individual writes when producing this data, then it's worth trying to
> replace '<< endl' with '<< "\n"' throughout this function.

That seems an easy change to make and might indeed make sense for the
inner loops. I'll time some things and see if it makes a difference for
me.

Cheers,

Mark