Re: [RFC][PATCH 0/5] NFS: trace points added to mounting path

Trond Myklebust
2009-01-21T22:56:18Z

On Thu, 2009-01-22 at 09:36 +1100, Greg Banks wrote:
> Chuck Lever wrote:
> >
> >
> > I think we need to visit this issue on a case-by-case basis.
> > Sometimes dprintk is appropriate. Sometimes printk(KERN_ERR).
> > Sometimes a performance metric.
> Well said.
>
> > Trond has always maintained that dprintk() is best for developers, but
> > probably inappropriate for field debugging,
> It's not a perfect tool but it beats nothing at all.
> > and I think that may also
> > apply to trace points.
> It depends on whether distros can be convinced to enable it by default,
> and install by default any necessary userspace infrastructure. The
> most important thing for field debugging is Just Knowing that you have
> all the bits necessary to perform useful debugging without having to
> find some RPM that matches the kernel that the machine is actually
> running now, and not the one that was present when the machine was
> installed.

Which is precisely why dprintk() is such a bad choice as a basis for a
set of trace points: every new patch and bugfix that the distro applies
will result in a reshuffling of the trace points as code is cleaned up
and moved around or removed entirely.

Cheers
Trond