Re: [PATCH v7 04/17] tracing: add static function tracer supportfor MIPS

[Maciej W. Rozycki]

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
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