RHEL5 服务器上 gettimeofday 的奇怪行为

RHEL5 服务器上 gettimeofday 的奇怪行为

我在 RHEL5 上遇到了 Time::HiRes 的非常奇怪的行为。由于 Time::HiRes 位于 Perl 标准安装中,并且基本上是 gettimeofday 系统调用的包装器,因此我倾向于将问题归咎于操作系统,而不是模块,甚至是 perl。

这是我的示例代码:

#!/usr/bin/perl

use Time::HiRes;
use LWP::Simple;

for (1..10) {

    my $started = [Time::HiRes::gettimeofday];

    # do something that we can expect to take time, but not too much time
    my $throwaway = get("http://localhost/");

    my $elapsed = Time::HiRes::tv_interval($started);

    print "$elapsed\n";

    sleep(1);

}

在我的 Mac 上运行此程序得到了完全合理的结果:

0.025934
0.000642
0.000716
0.001003
0.001026
0.000733
0.000815
0.000646
0.000629
0.000793

但在我的 RHEL5 服务器上运行却产生了不合理的结果:

0.034182
0.015998
0.06415
0.015523
-0.000379
0
0
0
0
0

特别注意第五个结果!

为了以防万一,以下是服务器上 perl -V 的结果:

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=linux, osvers=2.6.18-92.1.6.el5, archname=i686-linux
    uname='linux 188186.sexton.article7.co.uk 2.6.18-92.1.6.el5 #1 smp fri jun 20 02:36:16 edt 2008 i686 athlon i386 gnulinux '
    config_args='-des -Dprefix=/usr/local'
    hint=previous, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2',
    cppflags='-fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    ccversion='', gccversion='4.1.2 20071124 (Red Hat 4.1.2-42)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lnsl -ldl -lm -lcrypt -lutil -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=/lib/libc-2.5.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.5'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl): 
  Compile-time options: PERL_MALLOC_WRAP USE_LARGE_FILES USE_PERLIO
  Built under linux
  Compiled at Sep 15 2008 15:05:12
  @INC:
    /usr/local/perl/5.8.8/lib/5.8.8/i686-linux
    /usr/local/perl/5.8.8/lib/5.8.8
    /usr/local/perl/5.8.8/lib/site_perl/5.8.8/i686-linux
    /usr/local/perl/5.8.8/lib/site_perl/5.8.8
    /usr/local/perl/5.8.8/lib/site_perl
    .

这是一个已知问题吗?非常感激接受任何想法。

答案1

看一下

https://stackoverflow.com/questions/656537/is-there-a-better-way-to-determine-elapsed-time-in-perl

最后一条评论暗示这个问题不只你一个人有

答案2

您的系统速度如此之快,以至于在负时间内返回结果,您难道不为此感到高兴吗?:) 玩笑归玩笑,我们在虚拟化环境中遇到了 RHEL5 奇怪的时钟漂移问题;这与您的问题有关吗?

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