[PATCH] D58621: [XRay][tools] Pack XRayRecord - reduce memory footprint by a third. (RFC)

Mon Feb 25 13:25:14 PST 2019

lebedev.ri planned changes to this revision.
lebedev.ri added a comment.

In D58621#1409704 <https://reviews.llvm.org/D58621#1409704>, @dberris wrote:

> > This is a RFC because of the uint8_t CPU change.
> >  That chance needs discussing.
>
> So, this is an accident of history, which should be changed, but to the other direction. I've learned some time ago that it turns out there are some platforms that can have enough CPU IDs which can't be represented by a uint8_t. For future-proofing, we really should change this to be larger (`uint16_t`) and change basic mode to store 16-bit CPU IDs.

Boo :)
Unfortunately that won't just cost that one extra byte, it will have ripple effect on the padding in this struct.
I'm not sure as to exact numbers.

> The other parts seem fine to me, except for the potential churn on the user side (this is an ABI change).
> 
> I //think// that's fine for the C++ APIs, but that it will need some release notes (in case someone has been using the `Trace` API).

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D58621/new/

https://reviews.llvm.org/D58621