re: function ordering (was: Re: [RFC] exit_thread() speedups in x86

From: Dan Kegel
Date: Mon Jul 04 2005 - 08:45:46 EST


Arjan van de Ven wrote:
hmm. I wonder if a slightly different approach (based on the __slow)
idea would make sense
1) Use -ffunction-sections option from gcc to put each function in it's
own section
2) Use readprofile/oprofile data to collect an (external to the code)
list of hot/cold functions (we can put a default list in the kernel
source somewhere and allow people to measure their own if they want)
3) Use this list to make a linker script to order the functions

Somebody recently implemented something similar; see
http://www.bclennox.com/ldreorder/
It used valgrind rather than oprofile.
- Dan

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