Re: Sjlj vs dwarf2 on mingw for octave

[Tatsuro MATSUOKA]

Hello Bejamin

--- Benjamin Lindner wrote:

> Tatsuro MATSUOKA wrote:
> > The speed of binaries built with dw2 is 25 to 30 % faster than that of sjlj.
> > 
> > This is a just record so that I would not like to say dw2 EH is better than 
> > sjlj EH.
> 
> I'd go a step further and say, yes, regarding speed dw2 IS better than 
> sjlj. (It should be so by design.) dw2 is not flawless yet on windows, 
> but its speed bonus is not to be neglected.
> sjlj EH also slows down dynamic memory allocation using new/delete, 
> since this also involves exceptions.
> This is also the reason cygwin builds with gcc-3.3.3 were considerably 
> slower than builds with gcc-3.2 or (I guess) with new gcc-4 (where dw2 
> should be available again IIRC)

Thank you for your reply.

Regarding for speed of octave interpreter on mingw, the 25-30% speed up is not 
negligible.

In cygwin case, the slowness of sjlj is Incredibly large.  The speed of 
sjlj-octave interpreter is
about three to seven times slower than that of dw2.  This is not tolerable.  
Thus when I distributed
octave binaries on cygwin I built the octave binaries by specially configured 
gcc-3.4.4 with dw2 EH
built myself.

However, as you mentioned, dw2 is not flawless yet on windows.
This might be a reason why multithreaded ATLAS can be used only on sjlj EH.
The power of multithreaded atlas by pthread-win32 may be very large for large 
matrix calculations for
multicore cpu like Core2Duo and so on. The loss of 25-30% speed down in oxtave 
interpereter may be
trade-off.  I think that at present the selection of  either, sjlj or dw2, 
relies on users' purpose at
present.

I hope that dw2-EH will be flawless in the near future and multithreaded altlas 
will be able to be
used on octave built by GCC with dw2 EH.

Regards

Tatsuro 

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