Re: [PATCH 0/2] A kernel tracing interface

[Vara Prasad <prasadav@us.ibm.com>]

David Wilder wrote:

> Andrew Morton wrote:
>
> > On Thu, 13 Sep 2007 16:43:09 -0700
> > David Wilder <dwilder@us.ibm.com> wrote:
> >
> > > These patches provide a kernel tracing interface called "trace".
> > >
> > > The motivation for "trace" is to:
> > > - Provide a simple set of tracing primitives that will utilize the 
> > > high-
> > >   performance and low-overhead of relayfs for passing traces data from
> > >   kernel to user space.
> > > - Provide a common user interface for managing kernel traces.
> > > - Allow for binary as well as ascii trace data.
> > > - Incorporate features from the systemtap runtime that are
> > >   useful to others.
> > >
> > > History- Versions of this code have been submitted for review under
> > > a couple of different names.  The original submission was called UTT,
> > > it was later re-submitted as GTSC.   Christoph Hellwig commented "The
> > > code looks fine ...but the name is just dumb".  Following Christoph's
> > > advice, I changed the name to simply "Trace".
> > >
> > > This patch addresses review comments made by Christoph Hellwig and 
> > > Mathieu
> > > Desnoyers.  Changes include the addition of a mutex and synchronization
> > > protecting trace state changes (using RCU) and the reduction of the
> > > number of exports.
> > >
> > > Patches are against 2.6.23-rc4-mm1
> > >
> > > Required patches:
> > > 1/2 Trace code and documentation
> > > 2/2 Relay reset consumed  (required for trace's "rewind" feature")
> > >
> > > Signed-off-by: David Wilder <dwilder@us.ibm.com>
> >
> >
> > Well the code looks neat and easy enough to merge.
> >
> > What exactly is the relationship between this and systemtap and 
> > kprobes and
> > all the other tracing things which people are doing?
> The key to the relationship is relay.  Systemtap, kprobes, blktrace 
> ,(and others) need the fast user-kernel data hose that relay provides. 
> Trace is a means to simplify and standardize the use of relay. 
> Systemtap adopted this code some time ago in its own runtime.  Moving 
> this code into the kernel will allow other tracers to take advantage 
> of the same trace primitives.

Andrew,

This is part of the effort by the SystemTap team to move pieces of the 
project that are generic to mainline.

bye,
Vara Prasad

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