[Lldb-commits] [lldb] r105834 - in /lldb/trunk: include/lldb/Symbol/Symtab.h source/Symbol/Symtab.cpp

[Greg Clayton]

Great news. Try testing this same stuff after a "purge" (clear the file caches). The "purge" is not a great test, but it gives you a bit of an idea of how things would perform if nothing was in the file cache...

If things turn out the same as before, feel free to checkin the std::stable_sort fix.

Greg Clayton

On Jun 16, 2010, at 10:04 AM, Owen Anderson wrote:

> OK, I just performed these measurements on 64-bit 10.6, with both -Os and -O3 builds of lldb.  In both cases, std::sort was on the order of 50% slower than qsort_r:
> 
>                    -Os      -O3
> std::sort          0.118s   0.103s       
> qsort_r            0.077s   0.078s
> 
> However, here's the interesting part:
> 
> std::stable_sort   0.051s   0.048s
> 
> So, it looks like the symbol tables are already mostly sorted, and a simple insertion sort is able to "complete" the sort quickly.  FWIW, this would also be a good place to apply TimSort or some other heuristic sort.
> 
> --Owen
> 
> 
> On Jun 16, 2010, at 9:27 AM, Greg Clayton wrote:
> 
>> We start with "Sketch" from the /Developer/Expamples. It loads 91 shared libraries right off the bat, and if you then type:
>> 
>> (lldb) log timers enable
>> (lldb) breakpoint set --name main
>> (lldb) log timers disable
>> 
>> All of the symbol tables will be pulled in, and it will dump the timing information. 
>> 
>> You will first need to add a scoped timer to the top of:
>> 
>> Symtab::SortSymbolIndexesByValue()
>> 
>> The easiest way is:
>> 
>>     Timer scoped_timer (__PRETTY_FUNCTION__,__PRETTY_FUNCTION__);
>> 
>> Then you should see an entry in the timer dump for Symtab::SortSymbolIndexesByValue when the "log timers disable" is run with a total time.
>> 
> 
> 

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