Re: [Ksummit-2008-discuss] DTrace

[Joel Becker <Joel.Becker@oracle.com>]

On Tue, Jul 01, 2008 at 07:13:27PM -0400, Theodore Tso wrote:
> And remember, for the average kernel developer, the question is
> whether using SystemTap is easier than inserting a bunch of printk's

	I'll throw in a datapoint here.  I recently had to track a
problem down on a distro kernel, and rebuilding distro kernels takes a
lot of time.  So I decided to try SystemTap.  Once I'd discovered the
magic location of the distro's debuginfo package, systemtap was *WAY*
faster than prink+recompile.  I mean, we're talking 30 second turnaround
between "Oh, I'd like to print this other value" and actually printing
it.  In the core kernel, not a module.  No reboot, no nothin.  This is a
huge win.
	But I'll never replicate that for my normal work at this rate.
I'm usually floating multiple hand-built mainline kernels with new
work.  Just like Ted describes.

> repository or weekly automated snapshots.)  So actually, being able to
> install stripped modules and vmlinux into /boot and /linux, and then
> being able to put the unstripped binaries somewhere else, without
> having to use the !@#@! complicated RPM macros by Fedora/RHEL is
> actually **very** important to me.

	Me too.  I want to be able to say "make install; make
tap_install" in my kernel objdir.  "install" does what it always has
done - no change.  "tap_install" (or whatever) drops things in eg
/lib/modules/<version>/debug such that systemtap Just Works.  It can
error if systemtap isn't installed or is too old.  But I shouldn't have
to build a distro package of my kernel, or even understand the
mechanism for building 'debuginfo' bits (even if I do).

Joel

-- 

"I am working for the time when unqualified blacks, browns, and
 women join the unqualified men in running our overnment."
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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127