From f7231263d47beb4d7eba7eec4231e69967e156cf Mon Sep 17 00:00:00 2001
From: Martin Reddy <lynx@lindenlab.com>
Date: Wed, 9 Sep 2009 10:21:58 +0000
Subject: [PATCH] Fix for DEV-39442: Increased the performance of
LLDate::toHTTPDateString by over 50 times.
Looking at the usage, toHTTPDateStream is not called anywhere (except
internally by toHTTPDateString), and toHTTPDateString is called only
once outside of lldate.cpp, by LLStringUtil::formatDatetime. Also, the
method is most commonly called with a single two-character token, such
as "%Y" or "%A".
I therefore removed toHTTPDateStream and optimized toHTTPDateString.
Setting the locale was the most expensive operation, so I looked into
caching that, both in terms of std::ostream and strftime. The timings
for those implementations (averaged over 10 calls) is:
toHTTPDateString timings:
- with ostream (current) -> 0.314156 ms
- with ostream and std::locale caching -> 0.033999 ms
- with strftime and setlocale() caching -> 0.005985 ms
I therefore went with the standard C library strftime solution.
I also wrote a few unit tests to make sure that I didn't break any
existing functionality, and tested this under Windows and Linux.
Reviewed by steve.
---
indra/llcommon/lldate.cpp | 33 ++++++++++++++-------------------
indra/llcommon/lldate.h | 1 -
2 files changed, 14 insertions(+), 20 deletions(-)
diff --git a/indra/llcommon/lldate.cpp b/indra/llcommon/lldate.cpp
index 6a82a848bea..41150ad0577 100644
--- a/indra/llcommon/lldate.cpp
+++ b/indra/llcommon/lldate.cpp
@@ -38,7 +38,7 @@
#include "apr_time.h"
#include <time.h>
-#include <locale>
+#include <locale.h>
#include <string>
#include <iomanip>
#include <sstream>
@@ -100,33 +100,28 @@ std::string LLDate::toHTTPDateString (std::string fmt) const
{
LLFastTimer ft1(FT_DATE_FORMAT);
- std::ostringstream stream;
time_t locSeconds = (time_t) mSecondsSinceEpoch;
struct tm * gmt = gmtime (&locSeconds);
-
- stream.imbue (std::locale(LLStringUtil::getLocale().c_str()));
- toHTTPDateStream (stream, gmt, fmt);
- return stream.str();
+ return toHTTPDateString(gmt, fmt);
}
std::string LLDate::toHTTPDateString (tm * gmt, std::string fmt)
{
LLFastTimer ft1(FT_DATE_FORMAT);
-
- std::ostringstream stream;
- stream.imbue (std::locale(LLStringUtil::getLocale().c_str()));
- toHTTPDateStream (stream, gmt, fmt);
- return stream.str();
-}
-void LLDate::toHTTPDateStream(std::ostream& s, tm * gmt, std::string fmt)
-{
- LLFastTimer ft1(FT_DATE_FORMAT);
+ // avoid calling setlocale() unnecessarily - it's expensive.
+ static std::string prev_locale = "";
+ std::string this_locale = LLStringUtil::getLocale();
+ if (this_locale != prev_locale)
+ {
+ setlocale(LC_TIME, this_locale.c_str());
+ prev_locale = this_locale;
+ }
- const char * pBeg = fmt.c_str();
- const char * pEnd = pBeg + fmt.length();
- const std::time_put<char>& tp = std::use_facet<std::time_put<char> >(s.getloc());
- tp.put (s, s, s.fill(), gmt, pBeg, pEnd);
+ // use strftime() as it appears to be faster than std::time_put
+ char buffer[128];
+ strftime(buffer, 128, fmt.c_str(), gmt);
+ return std::string(buffer);
}
void LLDate::toStream(std::ostream& s) const
diff --git a/indra/llcommon/lldate.h b/indra/llcommon/lldate.h
index 23d3b900f8c..9dcce9117f3 100644
--- a/indra/llcommon/lldate.h
+++ b/indra/llcommon/lldate.h
@@ -86,7 +86,6 @@ class LLDate
void toStream(std::ostream&) const;
std::string toHTTPDateString (std::string fmt) const;
static std::string toHTTPDateString (tm * gmt, std::string fmt);
- static void toHTTPDateStream(std::ostream&, tm *, std::string);
/**
* @brief Set the date from an ISO-8601 string.
*
--
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