FORTIFY_SOURCE for the kernel

[Arjan van de Ven]

> References? Which CPUs? How generalizable are these results?
> 
> The fact that some applications might be running faster -Os-compiled,
> doesn't mean much.


there is 2 sorts of speed in this regard
1) local speed, eg the microbenchmark kind of measurement
2) system speed, which is taking an entire OS into account and not just
the local tight loops

-Os is undeniably good for 2), most likely to the point where it beats
performance. For the kernel it's -Os for a long time already, simply
because kernel memory has an even higher price since it's not pagable...

Most benchmarks you find for compilers do 1) without regard for 2) at
all, and the results can then be very deceptive.