[perl #121259] Slow global pattern match on specific large utf8 input

On Sun Feb 16 22:30:14 2014, perl5-porters@perl.org wrote:
> I wrote:
> > Now, why is the buffer that small?  I thought we were allocating an
> > extra byte for the sake of copy-on-write.
> 
> The extra byte is not added if we happen to have a nice large power
> of two.  Since sv_gets is allocating the string here (the assignment
> is optimised away and the input is read straight into $input), we can
> simply add a byte there, since we know we do not need a power of two.
> 
> Please try the sprout/121259 branch.  It seems to work for me.  (I
> still need to write a real commit message and comment the code.)

This fixed the performance for me, from:

real    3m58.732s
user    3m56.659s
sys     0m0.796s

to:

real    0m0.590s
user    0m0.236s
sys     0m0.176s

Tony


---
via perlbug:  queue: perl5 status: open
https://rt.perl.org/Ticket/Display.html?id=121259

• [perl #121259] Slow global pattern match on specific large utf8 input by Father Chrysostomos via RT
• [perl #121259] Slow global pattern match on specific large utf8 input by Tony Cook via RT