Re: [linus:master] [fortify] 239d87327d: vm-scalability.throughput 17.3% improvement

[Kees Cook]

On Thu, Jan 09, 2025 at 08:51:44AM -0800, Kees Cook wrote:
> On Thu, Jan 09, 2025 at 02:57:58PM +0800, kernel test robot wrote:
> > kernel test robot noticed a 17.3% improvement of vm-scalability.throughput on:
> > 
> > commit: 239d87327dcd361b0098038995f8908f3296864f ("fortify: Hide run-time copy size from value range tracking")
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 
> Well that is unexpected. There should be no binary output difference
> with that patch. I will investigate...

It looks like hiding the size value from GCC has the side-effect of
breaking memcpy inlining in many places. I would expect this to make
things _slower_, though. O_o

-- 
Kees Cook