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Re: Patch to make string-append on win32 100 times faster

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August 2, 2010 03:26
Re: Patch to make string-append on win32 100 times faster
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On 31 July 2010 17:04, Nicholas Clark <> wrote:
> On Fri, Jul 30, 2010 at 11:26:15PM +0200, wrote:
>> From: Marvin Humphrey <>
>> Date: 30.07.2010 17:34
>> >>* Why the "+10"?  Why have a extra minimum at all?  Why "10" instead
>> >>of another number?  Given your examples, for a large string the 10 is
>> >>a trivial fraction of the total and for a small string, the efficiency
>> >>either doesn't matter or the string quickly grows into a large string
>> >>anyway.
>> >>
>> >
>> >That's similar to my analysis.  I think it's more useful to round up to a
>> >multiple of the pointer size for small values.
>> >
>> If I understand correctly (which I'm not certain about), this is done
>> anyway right afterwards in
>> newlen = PERL_STRLEN_ROUNDUP(newlen);
> That's certainly what the expression in PERL_STRLEN_ROUNDUP() is intended to
> do. (Round up to a multiple of the pointer size, so that growth of strings by
> small amounts usually avoids repeated realloc() calls for an extra 1 or 2
> bytes).

When i saw this I was confused, as I remember when Nicholas wrote the
patch that added PERL_STRLEN_ROUNDUP(), and Im wondering why this
patch doesnt modify /that/ instead of adding additional logic /in
front/ which will then be mixed together....

IOW, it seems like this patch will add some percentage, and then
PERL_STRLEN_ROUNDUP will add another percentage of /that/.

This doesnt seem right. Whats the problem PERL_STRLEN_ROUNDUP(), and,
given that PERL_STRLEN_ROUNDUP() is guarded like so:

#ifndef Perl_safesysmalloc_size
   newlen = PERL_STRLEN_ROUNDUP(newlen);

why should this new logic not also be guarded? Surely the intent is to
have a mode where Perl doesnt mess with requested size at all?


perl -Mre=debug -e "/just|another|perl|hacker/"

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