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gprof extreemly slow on reading a 64bit executable

From: Dirk-Jan Jongeneel
Subject: gprof extreemly slow on reading a 64bit executable
Date: Thu, 09 Feb 2006 10:13:07 +0100
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040616

I have a large program compiled on rh72 as well as rhel3 using gcc3.2.3 or gcc4.0.2 (I use -fno-omit-frame-pointer in 64bit case else it would not work at all there - but that seems to be a known issue) I use binutils-

If I run gprof <executable> for the 32 bit it returns in 30 seconds with no gmon.out. If I do that for the 64bit version it takes 25 min!!

I have also tried with binutils-2.16.1. and ran profile and gdb.

I see the following difference between the 32bit read and 64bit read.
_bfd_elf_find_nearest_line in elf.c calls

in case of 32bit it returns with true but in case of 64bit it fails and eventually calls
elf_find_function at the end.
It calls this thousands of times and spends 95% of cputime in there.

So the cause of slownes seems a problem in _bfd_dwarf2_find_nearest_line not being able to find what it needs.

What can I do to debug/fix this issue?



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