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[Bug libc/15943] New: localtime_r performance drop when set different timezone
- From: "qd dot feng at alcatel-lucent dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Wed, 11 Sep 2013 02:20:10 +0000
- Subject: [Bug libc/15943] New: localtime_r performance drop when set different timezone
- Auto-submitted: auto-generated
https://sourceware.org/bugzilla/show_bug.cgi?id=15943
Bug ID: 15943
Summary: localtime_r performance drop when set different
timezone
Product: glibc
Version: 2.12
Status: NEW
Severity: normal
Priority: P2
Component: libc
Assignee: unassigned at sourceware dot org
Reporter: qd.feng@alcatel-lucent.com
CC: drepper.fsp at gmail dot com
There is one thread in our application frequently call the localtime_r. We
found the thread performance has 20% drop when change the timezone from the
America/New_york to Asia/Shanghai from the system(Redhat 6,). After profile, we
found it is the localtime_r cause the difference.
When set the timezone as America/New_york, the __tzfile_compute mainly call the
__tzstring. While when set the timezone as the Asia/Shanghai the
__tzfile_compute call the __tzset_parse_tz which consume most of the CPU time.
I also do an simple test on our HP G8 server.
1 #include <time.h>
2 #include <stdio.h>
3
4 int main(void)
5 {
6 struct tm newtime;
7 time_t ltime;
8 char buf[50];
9
10 for(int i=0;i<=1000000;i++)
11 {
12 ltime=time(<ime);
13
14 localtime_r(<ime, &newtime);
15 }
16 }
After compile and run command time ./a.out with the timezone as Asia/Shanghai
or
America/New_York.
Asia/Shanghai
real 0m1.838s
user 0m1.628s
sys 0m0.206s
America/New_York
real 0m0.608s
user 0m0.395s
sys 0m0.211s
There is no TZ env been set on both cases. I wonder what causes the performance
so difference, is it an designed behavior?
Steven
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