Enhanced profiling support (was Re: vm lock contention reduction)

[John Levon]

[Excuse the quoting, I was out of the loop on this ...]

On Sat, Jul 06, 2002 at 08:47:54PM -0700, Andrew Morton wrote:

> Linus Torvalds wrote:
> > 
> > I haven't had much time to look at the oprofile thing, but what I _have_
> > seen has made me rather unhappy (especially the horrid system call
> > tracking kludges).

It makes me very unhappy too. There are a number of horrible things
there, mostly for the sake of convenience and performance.
sys_call_table is just the most obviously foul thing.  I'm glad to hear
there is interest in getting some kernel support for such things to be
done tastefully.

> > I'd rather have some generic hooks (a notion of a "profile buffer" and
> > events that cause us to have to synchronize with it, like process
> > switches, mmap/munmap - oprofile wants these too), and some generic helper
> > routines for profiling (turn any eip into a "dentry + offset" pair
> > together with ways to tag specific dentries as being "worthy" of
> > profiling).

How do you see such dentry names being exported to user-space for the
profiling daemon to access ? The current oprofile scheme is, um, less
than ideal ...

> So.  John.  Get coding :-)

I'm interested in doing so but I'd like to hear some more on how people
perceive this working. It essentially means a fork for a lot of the
kernel-side code, so it'd mean a lot more work for us (at least until I
can drop the 2.2/2.4 versions).

regards
john

-- 
"If a thing is not diminished by being shared, it is not rightly owned if
 it is only owned & not shared."
	- St. Augustine