lkml.org 
[lkml]   [2010]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [ANNOUNCE] New utility: 'trace'

* Darren Hart <dvhart@linux.intel.com> wrote:

> On 11/16/2010 01:04 PM, Thomas Gleixner wrote:
> >We are pleased to announce a new tracing tool called 'trace'.
> >
>
> Hi Thomas, Ingo - Congrats and Thanks!

You are welcome :)

> > At this point we'd like to ask for feedback from other users of tracing tools,
> > which workflow components would you like to see in addition to what the 'trace'
> > tool is offering?
> >
> > Comments, bug reports, suggestions welcome,
>
> The first thing that comes to mind is trace_marker:
>
> echo "Test point A" > /sys/kernel/debug/tracing/trace_marker
>
> I've found this sort of markup to be useful using ftrace (with C equivalents
> embedded in the test case). Is this supported?

Yes, LatencyTop uses something similar IIRC, via a prctl() hack: it uses
prctl(PR_SET_NAME) to inject up to 16 characters into the comm - and then every perf
event gets that comm. You can utilize that straight away if you need a marker
solution right now.

A cleaner, more generic approach would be a more free-form ASCII event facility for
this: a generic 'user-space triggered event' with injection capabilities.

To inject it, we could put that into a prctl() as well, for easy, single-syscall
access from C. We already have two perf prctls: PR_TASK_PERF_EVENTS_DISABLE,
PR_TASK_PERF_EVENTS_ENABLE - and this would be a third one: PR_TASK_PERF_USER_EVENT.

This would, like the existing perf_event_task_enable()/disable() methods, loop
through current events and inject a string into matching user events.

Ideally i'd like to see basically user-space access to trace_printk(), and proper
integration into /debug/tracing/events/ enumeration and availability - not a
ftrace-specific and admin-only hack like /sys/kernel/debug/tracing/trace_marker is
today.

Would you be interested in helping out with (and testing) such a more generic
approach?

Thanks,

Ingo


\
 
 \ /
  Last update: 2010-11-16 23:03    [W:0.556 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site