On Fri, 25 Jan 2013 09:11:01 -0500, ling.ma.prog...@gmail.com said: > Based on above reasons, we compiled linux kernel 3.6.9 with O2 and Os > respectively. The results show Os improve performance netperf 4.8%, > 2.7% for volano as below
Am I allowed to NAK this? What the numbers given so far *actually* show is 4.8% more instructions executed, *not* 4.8% better performance. I'm having a *very* hard time convincing myself that what we're seeing isn't simply the expected behavior of loops *not* being unrolled and similar non-optimizations done by -Os, so more instructions get executed to do the same amount of work. Rather than "run for 10 seconds and count instructions", can we "run for 50,000 syscalls and count clock time" or similar that shows an *actual* improvement?
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