Re: [RFC/patch] Sort global symbols in psymtabs only if needed

[Aleksandar Ristovski <aristovski@qnx.com>]

Daniel Jacobowitz wrote:
> On Mon, Feb 11, 2008 at 11:19:46AM -0500, Aleksandar Ristovski wrote:
>> The attached patch sorts on first lookup instead of on load.
> 
> Does this help if you benchmark any non-trivial debug sessions?
> You've sped up startup, but the first call to lookup_symbol is going
> to search a large number of such psymtabs.
The full price will probably be paid with longer debug sessions, but it 
definitely improves time to "stopped in main".

> 
> Also, you probably know this, but be careful using gprof for this sort
> of thing.  I recommend oprofile.  gprof artificially inflates the cost
> of small frequent functions like strcmp_iw_ordered, because of all the
> overhead.
No, the delay really comes from there, I used wall-clock timings as well, but 
thought this is more representative.
> 
> The patch may still be a good idea.  Can we eliminate the binary
> search / sort entirely?  We do hash table lookups for full symtabs;
> that should be faster than sorting.  See dict_create_hashed.
> 
> Those are all hardwired to "struct symbol" at the moment.  But
> I think it only uses SYMBOL_SEARCH_NAME, so it could work with
> psymbols too if we passed the ginfo around.
> 
> 
I haven't investigated this, but I will take a look... So we would only hash and 
use hash lookup for both psymtabs and symtabs. It sounds to me as something doable.