On Wed, 11 Nov 2009, Wu Zhangjin wrote: > > -mlong-calls really degrades performance. I have seen things like 6% > > drop in network packet forwarding rates with -mlong-calls. > > > > so much drop? seems only two instructions added for it: lui, addi. from > this view point, I think the -fno-omit-frame-pointer(add, sd, move...) > will also bring with much drop. No, register jumps cannot be predicted -- this is where the performance goes on any serious processor -- the two extra instructions are nothing compared to that. OTOH frame pointer calculations are pure arithmetic, so you only lose time incurred by the instructions themselves. Maciej
