[Crash-utility] Re: Fix for source line numbers for x86_64 modules

On Wed, Sep 16, 2009 at 04:44:32PM -0600, Bob Montgomery wrote: > John and I think that this code in gdb searches things too many times, > particularly with this patch, but it's a start since it seems to fix the > problem. I'm attaching a new version of the patch, that performs way better when disassembling functions that live in the kernel. (Bob found that the original patch made crash disassemble in-kernel functions at least 3 times slower, but that number will be larger depending on how close the symbol table the function lives in is to the head of the psymtabs list. Module disassembly speed wasn't changed much at all.) With this updated patch, we found the performance penalty of "dis -l" to be marginal. The problem with the original patch is that once the address we want is found in a symbol table, it then looks through the rest of the symbol tables in that objfile for a better match. The original code would then return the best pst out of that objfile (and never get the next pst from ALL_PSYMTABS), but we want to go through the rest of the objfiles just in case, so I moved the return statement outside of the ALL_PSYMTABS loop. But the next pst from ALL_PSYMTABS will not be from a new objfile - so we would wind up traversing the list (minus one element) again, and again, and again... The new patch removes the inner list traversal, and just takes advantage of the fact that we already iterate through every pst via ALL_PSYMTABS.