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

Vara Prasad
2007-09-18T16:54:19Z

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