Re: [PATCH v2] tools/power turbostat: Fix RAPL summary collection on AMD processors
From: Chen Yu
Date: Fri Apr 23 2021 - 08:12:25 EST
On Tue, Apr 20, 2021 at 10:42:09AM -0400, Calvin Walton wrote:
> On Tue, 2021-04-20 at 22:37 +0800, Chen Yu wrote:
> > On Tue, Apr 20, 2021 at 09:28:06AM -0400, Calvin Walton wrote:
> > > This patch has the same issue I noticed with the initial revision
> > > of
> > > Terry's patch - the idx_to_offset function returns type int (32-bit
> > > signed), but MSR_PKG_ENERGY_STAT is greater than INT_MAX (or
> > > rather,
> > > would be interpreted as a negative number)
> > >
> > > The end result is, as far as I can tell, that it hits the if
> > > (offset <
> > > 0) check in update_msr_sum() resulting in the timer callback for
> > > updating the stat in the background when long durations are used to
> > > not
> > > happen.
> > >
> > > For short durations it still works fine since the background update
> > > isn't used.
> > >
> > Ah, got it, nice catch. How about an incremental patch based on Bas'
> > one
> > to fix this 'overflow' issue? Would converting offset_to_idx(),
> > idx_to_offset() and
> > update_msr_sum() to use off_t instead of int be enough? Do you or
> > Terry have interest
> > to cook that patch? For Terry's version, I'm not sure if spliting
> > the code into different CPU vendor would benefit in the future,
> > except
> > that we would have plenty of new MSRs to be introduced in the future.
> Yes, I believe updating the offset_to_idx(), idx_to_offset(), and
> update_msr_sum() functions is sufficient. I can do the incremental
> patch for that this evening if nobody beats me to it :)
Calvin, could you please take a look at the following version if it is suitible?