Re: [PATCH] perf, script: Minimize "not reaching sample" for brstackinsn

[Andi Kleen <ak@linux.intel.com>]

> > There are two common cases where the message is bogus:
> > - The LBR only logs taken branches, but the branch might be a
> > conditional branch that is not taken (that is the most common
> > case actually)
> 
> How do you know it is not a taken branch that missed the LBR update?

I don't, but the not taken case is totally valid (and also common)
so it doesn't make sense to have a mere sanity check make a common
case unusable.

> 
> > - The LBR sampling uses a filter ignoring some branches,
> > but the perf script check checks for all branches.
> 
> Not understanding this case.  Do you mean you expect not to reach
> the sample, so there is no point printing the message?

If the LBR is e.g. filtered on far branches it makes no sense to 
check for non far branches. There are lot of filtering cases here which
would be very complicated to handle for a mere sanity check,
so the best way is to not do the bogus sanity check.

-Andi