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Re: FORTIFY_SOURCE for the kernel



On Mon, 2006-01-23 at 09:05 -0600, Josh Boyer wrote:
> > On Mon, 2006-01-23 at 07:53 -0600, Josh Boyer wrote:
> >> > On Mon, 2006-01-23 at 11:30 +0900, Warren Togami wrote:
> >
> >> > Going off at a tangent....what would people think of the idea of
> >> > switching to -Os in $RPM_OPT_FLAGS _after_ FC5 is released?
> >>
> >> If it results in some form of improvement in performance, I'm all for
> >> it.
> >
> > The "s" in -Os stands for "size", not for "speed". So if -Os compiled
> > code-execution is faster than the default CFLAGS, something must be
> > broken elsewhere.
> 
> That's not true.  Yes, -Os stands for size.  However code size _can_
> translate to performance increase.
True, but this would mean -Os rsp. RPM_OPT_FLAGS having missed the
objectives they have been designed for.

But note that I referred to code execution speed, not application
performance.
 
>   Think about cache footprint, etc. 
> Smaller code means more can fit in the cache.  It also results in a
> smaller DRAM footprint for thinks like shared libraries, etc.
Right, there are other components interfering but the compiler's code
generation (prelink, shared-libraries, kernel, suboptimal code, cpu
performance, memory performance etc., etc.) on application performance

Identifying and keeping these issues apart, however is difficult.

Ralf



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