lkml.org 
[lkml]   [2007]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch-early-RFC 00/10] LTTng architecture dependent instrumentation

hi Mathieu,

* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> Hi,
>
> Here is the architecture dependent instrumentation for LTTng. [...]

A fundamental observation about markers, and i raised this point many
many months ago already, so it might sound repetitive, but i'm unsure
wether it's addressed. Documentation/markers.txt still says:

| * Purpose of markers
|
| A marker placed in code provides a hook to call a function (probe)
| that you can provide at runtime. A marker can be "on" (a probe is
| connected to it) or "off" (no probe is attached). When a marker is
| "off" it has no effect, except for adding a tiny time penalty
| (checking a condition for a branch) and space penalty (adding a few
| bytes for the function call at the end of the instrumented function
| and adds a data structure in a separate section).

could you please eliminate the checking of the flag, and insert a pure
NOP sequence by default (no extra branches), which is then patched in
with a function call instruction sequence, when the trace point is
turned on? (on architectures that have code patching infrastructure -
such as x86)

Ingo


\
 
 \ /
  Last update: 2007-12-06 12:09    [from the cache]
©2003-2011 Jasper Spaans