Re: [RFD 0/5] Add latency histogram

[Tom Zanussi <tom.zanussi@linux.intel.com>]

Hi Daniel,

On Thu, 2015-04-30 at 12:06 +0200, Daniel Wagner wrote:
> Hi,
> 
> I would like to discuss a possible way of getting the feature of the
> latecy_hist.patch [1] added to mainline.
> 
> "Latency histograms are primarily relevant in the context of real-time
> enabled kernels (CONFIG_PREEMPT/CONFIG_PREEMPT_RT)and are used in the
> quality management of the Linux real-time capabilities."
> 
> Steven pointed out that this might be doable based on Tom Zanussi's
> "[PATCH v4 0/7] tracing: 'hist' triggers" [2].
> 
> Here are my findings. It was not too complicated to get it working,
> though I had to add some hacks. I have added comments to each patch.
> 

It looks like you were able to do quite a bit here with not much code -
nice!

Just FYI, I'll be working on a v5 of the hist triggers patchset that
will incorporate the stuff from patch 1 (needs to be split into a
separate patch for the triggers code already upstream, and one for hist
triggers) and your comments from patch 2 (see comments in my reply to
that patch), along with  a couple other unrelated changes...

Tom

> cheers,
> daniel
> 
> [2] https://lkml.org/lkml/2015/4/10/591
> [1] https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit/?h=v3.14-rt-rebase&id=56d50cc34943bbba12b8c5942ee1ae3b29f73acb
> 
> Daniel Wagner (4):
>   tracing: Add support to sort on the key
>   tracing: Add option to quantize key values
>   tracing: Deference pointers without RCU checks
>   tracing: Add trace_irqsoff tracepoints
> 
> Tom Zanussi (1):
>   tracing: 'hist' triggers
> 
>  include/linux/rculist.h             | 36 +++++++++++++++++++++++++++++
>  include/linux/tracepoint.h          |  4 ++--
>  include/trace/events/latency.h      | 40 ++++++++++++++++++++++++++++++++
>  kernel/trace/trace_events_hist.c    | 46 +++++++++++++++++++++++++++++++++----
>  kernel/trace/trace_events_trigger.c | 18 +++++++++------
>  kernel/trace/trace_irqsoff.c        | 38 ++++++++++++++++++++++++++++++
>  6 files changed, 168 insertions(+), 14 deletions(-)
>  create mode 100644 include/trace/events/latency.h
>