[PATCH] _dl_find_hash: optmizie symbol lookup delaying stringcomparisons

[Joakim Tjernlund]

> -----Original Message-----
> From: Carmelo AMOROSO [mailto:carmelo.amoroso at st.com] 
> Sent: den 4 oktober 2007 20:00
> To: Joakim Tjernlund
> Cc: uclibc
> Subject: Re: [PATCH] _dl_find_hash: optmizie symbol lookup 
> delaying stringcomparisons
> 
> Joakim Tjernlund wrote:
> > Hi Carmelo
> >
> > This has been up before and I am not convinced it is a gain.
> > The if (sym->st_value == 0) and if 
> (ELF_ST_TYPE(sym->st_info) > STT_FUNC)
> > are mostly false.
> >
> > Suggest you get some numbers before applying this patch.
> >
> > Jocke
> >
> Joakim Tjernlund wrote:
> > Hi Carmelo
> >
> > This has been up before and I am not convinced it is a gain.
> > The if (sym->st_value == 0) and if 
> (ELF_ST_TYPE(sym->st_info) > STT_FUNC)
> > are mostly false.
> >
> > Suggest you get some numbers before applying this patch.
> >
> > Jocke
> >
> Hi Jocke, here they are the numbers you were asking for ;-)
> 
> I've run the uClibc testsuite (using sh4 nptl as usual for me :-) )
> to collect data.
> 
> I've executed them (316 tests) in 4 different scenarios:
> 
> 1) SysV hash - *no* strcmp patch
> 2) SysV hash - *with* strcmp patch
> 3) GNU hash - *no* strcmp patch
> 4) GNU hash - *with* strcmp patch
> 
> To get figures, I have hacked the ld.so adding a variable
> to count how many times the ld.so calls a strcmp to check
> for a symbol matching and it fails, printing it to stderr
> before the linker passes the control to the application.

I hope you linked/run with LD_BIND_NOW enabled, else you miss all JMP_SLOT calls

your table at the end is somewhat corrupted, but from your description
I conclude that it is mostly a win for SysV and always for GNU Hash so
feel free to make the change.

  Jocke