Poor date() performance (v 5.4.9) [PATCH] View as Markdown

Hi,

2012/12/1 Paul Taulborg njaguar@gmail.com

I am migrating from 4.4.9 to some new servers I built out, and wrote a
benchmark suite that is testing many individual aspects of PHP so I
could see what sort of performance benefits I might see not only from
the new server, but moving off my custom forked 4.4.9 branch. Here's a
snippet of some of the comparisons: (sorry for the poor formatting) --
each test is run using 1 million loops.

4.4.9 on old machine vs 5.4.9 on new machine:
for : 0.213 sec for : 0.019 sec
while : 0.145 sec while : 0.014 sec
if else : 0.449 sec if else : 0.069 sec
switch : 0.547 sec switch : 0.087 sec
Ternary : 0.418 sec Ternary : 0.066 sec
str_replace : 1.043 sec str_replace : 0.421 sec
preg_replace : 3.627 sec preg_replace : 1.678 sec
preg_match : 1.250 sec preg_match : 0.509 sec

As you can see, the new machine is considerably faster, and there are
no major issues with wanting to switch... until I get to the date
functions I make frequent use of:
date : 1.856 sec date : 2.111 sec
strtotime : 2.963 sec strtotime : 3.133 sec

and just to test (though I don't currently use it):
strftime : 2.679 sec strftime : 1.764 sec

The former two actually are slower on the new box and newer version of
php, when everything else is 2 to 200x faster.

Relevant code to the functions: (tested with and without the $now
parameter -- which makes no perceptible difference)
date('F j, Y, g:i a', $now);
strftime('%B %e, %Y, %l:%M %P', $now);

This type of formatting is pretty common. I started digging into the
source code, and found an obvious place where there was a performance
issue:
timelib_isoweek_from_date(t->y, t->m, t->d, &isoweek, &isoyear);
is being called every time, even though it's only used in two rather
obscure cases, and ones that are probably very uncommon in actual
practice. So, to test, I created a "is set" type variable, and moved
the function call into each case, with a condition checking if it was
already populated, if not, call the function to populate isoweek and
isoyear, then resume as before. (Patch will be attached as a file)

I then recompiled and reran my benchmark and here is the result:
date: 1.763 sec
Which is a performance increase of nearly 20%.

My patch was thrown together rather quickly to just do a quick test,
so it may warrant some tweaking before being applied to any branches.
I plan to continue digging, as I feel that I should be able to
continue to improve the performance of these functions further. The
rest will be a little less obvious, is there is much more cross
functionality issues to contend with to ensure nothing is broken.

Side note- I attempted the same concept with not setting the timezone
information if those flags were not used in the switch (which they
aren't in anything I use), but it didn't appear to have any noticeable
performance increase. My next step is to start tracing through actual
execution and see if I can't find any other obvious issues. My initial
thoughts are that it may be faster to try and cache some of this (for
fcgi purposes), or even have a compile time option to allow a build to
use old 4.4.9 functionality that uses localtime_r() and actually
trusts that the server has the right information set.

Thanks in advance for looking at this with me!

As far I remember, the patch must be in a .txt extension to be sent to the
list.

Thanks.

--
Regards,
Felipe Pena

My apologies, pasting the patch in directly:

--- php-5.4.9_orig/ext/date/php_date.c 2012-11-20 23:12:20.000000000 -0600
+++ php-5.4.9/ext/date/php_date.c 2012-12-01 05:38:22.136264276 -0600
@@ -948,6 +948,7 @@
timelib_time_offset *offset = NULL;
timelib_sll isoweek, isoyear;
int rfc_colon;

• char weekYearSet = 0;

  if (!format_len) {
  return estrdup("");
  @@ -974,7 +975,6 @@
  offset = timelib_get_time_zone_info(t->sse, t->tz_info);
  }
  }

• timelib_isoweek_from_date(t->y, t->m, t->d, &isoweek, &isoyear);

  for (i = 0; i < format_len; i++) {
  rfc_colon = 0;
  @@ -990,8 +990,12 @@
  case 'z': length = slprintf(buffer, 32, "%d", (int)
  timelib_day_of_year(t->y, t->m, t->d)); break;

  	/* week */
  

•   	case 'W': length = slprintf(buffer, 32, "%02d", (int) isoweek);
  

break; /* iso weeknr */

•   	case 'o': length = slprintf(buffer, 32, "%d", (int) isoyear);
  

break; /* iso year */

•   	case 'W':
  

•   		if(!weekYearSet) { timelib_isoweek_from_date(t->y, t->m, t->d,
  

&isoweek, &isoyear); weekYearSet = 1; }

•   		length = slprintf(buffer, 32, "%02d", (int) isoweek); break; /*
  

iso weeknr */

•   	case 'o':
  

•   		if(!weekYearSet) { timelib_isoweek_from_date(t->y, t->m, t->d,
  

&isoweek, &isoyear); weekYearSet = 1; }

•   		length = slprintf(buffer, 32, "%d", (int) isoyear); break; /* iso year */
  
    	/* month */
    	case 'F': length = slprintf(buffer, 32, "%s", mon_full_names[t->m
  

• 1]); break;