Re: VERBOSE flags

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Tue, Sep 20, 2016 at 12:11:40PM +0000, Dalessandro, Dennis wrote:
> On Tue, 2016-09-20 at 13:56 +0300, Leon Romanovsky wrote:
> > > Yes we do have that, which illustrates that trace points can not do
> > > everything. I had hoped to deprecate that at some point.
> > > Regardless,
> > > sometimes you want additional code to be added or to do something
> > > slightly different. You can't do that with a tracepoint.
> >
> > Can you elaborate more on this topic? Which limitations did you see
> > in tracepoints?
>
> Just making up an example. Say you have a hash table. You want to dump
> the items. If you iterate over it and do a trace point, yeah the actual
> trace point has little to no perf impact, but you still walk the
> table. 
>
> There are situations where you need to do more for debugging than just
> printing a message. 

Thanks

>
> > In regards of other discussion in KS 2016, "tracepoints and ABI
> > stability warranties" [1]. Are you strict with this tracepoints ABI?
>
> Honestly we are not super strict about it, but do take care not to
> break/remove something that could be useful. It will be interesting to
> see what comes out of the discussion. Perhaps we do need to be more
> strict about them going forward.

I followed the discussion and it looks like that majority are against to
declare tracepoints as ABI. Otherwise, you will find yourself unable to
change the kernel code.

>
> -Denny

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