dovecot - Aug 2010 - Why p_strdup and other string functions uses loops instead strlen? (dovecot 2.0.rc4)

I did Dovecot profiling on huge e-mail system, and p_strdup was very 
high on list.

I do minor change:
p_strdup:
/*
	for (len = 0; (str)[len] != '\0'; )
		len++;
	len++;
*/
	len = strlen(str) + 1;

p_strndup:
/*
	len = 0;
	while (len < max_chars && ((const char *) str)[len] != '\0')
		len++;
*/
	len = strnlen(str, max_chars);

And after changes strdup drop down on the profile list.


This is output from oprofile:

samples  %        symbol name
28000    10.9764  p_strdup
8507      3.3349  safe_memset
7857      3.0801  .plt
7627      2.9899  buffer_write
6871      2.6935  parse_body_add_block

And after (about four times smaller samples, but shows everything):
samples  %        symbol name
9595     26.2625  parse_next_body_to_boundary
8247     22.5729  parse_body_add_block
772       2.1130  .plt
672       1.8393  buffer_write
658       1.8010  __i686.get_pc_thunk.bx
614       1.6806  safe_memset
586       1.6039  pool_alloconly_malloc
559       1.5300  p_strdup
533       1.4589  hash_table_insert_node


I wonder why You use loops instead strlen, which is optimalised on every 
platforms.

Redgards,
Len7hir

On 10.8.2010, at 10.30, Len7hir wrote:
> I did Dovecot profiling on huge e-mail system, and p_strdup was very high
on list.
> 
> I do minor change:
> p_strdup:
> /*
> 	for (len = 0; (str)[len] != '\0'; )
> 		len++;
> 	len++;
> */
> 	len = strlen(str) + 1;
Committed: http://hg.dovecot.org/dovecot-2.0/rev/7f550a7bd9d7
> p_strndup:
> /*
> 	len = 0;
> 	while (len < max_chars && ((const char *) str)[len] !=
'\0')
> 		len++;
> */
> 	len = strnlen(str, max_chars);
strnlen() exists only in Linux and FreeBSD, so if this change is made it has to
be behind #ifdef HAVE_STRNLEN. But if it was only p_strdup() that was on the
profile listing, it's a bit too much trouble to add support for it.
> I wonder why You use loops instead strlen, which is optimalised on every
platforms.
No reason. I guess the excuse is that it was written 8-9 years ago.