C++11 setrlimit RLIMIT_CPU引发的SIGXCPU晚于虚拟机中的预期时间

[编辑：在文本中添加MCVE，澄清]

我有以下程序，它使用

setrlimit（）

将

RLIMIT\u CPU

设置为2秒，并捕获信号<代码>限制CPU时间。«当进程达到软限制时，将发送一个

SIGXCPU

信号。此信号的默认操作是终止进程。但是，可以捕获信号，处理程序可以将控制权返回主程序。»（）

下面的程序为

SIGXCPU

设置

RLIMIT\u CPU

和信号处理程序，然后它生成随机数，直到

SIGXCPU

升高，信号处理程序仅退出程序

测试信号.cpp

/*
*CMS上信号处理的测试程序。
*
*编译时使用：
*/usr/bin/g++[-DDEBUG]-Wall-std=c++11-O2-pipe-static-s\
*-o测试\信号测试\信号.cpp
*
*选项-DDEBUG激活helpers库中的一些调试日志记录。
*/
#包括
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#包括
#包括
使用名称空间std；
命名空间帮助程序{
长启动时间=-1；
易失性信号原子超时标志=false；
unsigned const timelimit=2；//CPU时间的软限制（秒）
无效设置信号（无效）；
作废设置\时限\作废；
静态无效信号处理器（int信号）；
长获取时间（无效）；
bool已达到超时（无效）；
作废设置（作废）；
}
名称空间{
无符号常数minrand=5；
无符号常量maxrand=20；
int const numcycles=5000000；
};
/*
*非常简单的调试器，在编译时使用-DDEBUG启用。
*如果启用，它将在stderr上打印，否则它什么也不做（它不会
*甚至计算表达式的右侧）。
*
*主要思想来自：
*-C++启用/禁用STD：调试的调试消息
*     (https://stackoverflow.com/q/3371540/2377454)
*-标准无操作输出流
*     (https://stackoverflow.com/a/11826787/2377454)
*/
#ifdef调试
#定义调试为真
#否则
#定义调试错误
#恩迪夫
#如果（！debug），则定义debug_记录器\
{} \
否则\
瑟尔
/usr/bin/g++ -DDEBUG -Wall -std=c++11 -O2 -pipe -static -s -o test_signal test_signal.cpp

$ /usr/bin/time -v  ./test_signal                                                                     
[DEBUG] helpers::set_signal:    set_signal() called
[DEBUG] helpers::set_signal:    action.sa_handler: 1
[DEBUG] helpers::set_limit:     set_limit() called
[DEBUG] helpers::set_limit:     current limit: 2 seconds
i: 0    - nmsec: 11 - program has been running for 150184 microseconds
i: 1    - nmsec: 18 - program has been running for 294497 microseconds
i: 2    - nmsec: 9  - program has been running for 422220 microseconds
i: 3    - nmsec: 5  - program has been running for 551882 microseconds
i: 4    - nmsec: 20 - program has been running for 685373 microseconds
i: 5    - nmsec: 16 - program has been running for 816642 microseconds
i: 6    - nmsec: 9  - program has been running for 951208 microseconds
i: 7    - nmsec: 20 - program has been running for 1085614 microseconds
i: 8    - nmsec: 20 - program has been running for 1217199 microseconds
i: 9    - nmsec: 12 - program has been running for 1350183 microseconds
i: 10   - nmsec: 17 - program has been running for 1486431 microseconds
i: 11   - nmsec: 13 - program has been running for 1619845 microseconds
i: 12   - nmsec: 20 - program has been running for 1758074 microseconds
i: 13   - nmsec: 11 - program has been running for 1895408 microseconds
[DEBUG] helpers::signal_handler:    signal 24 received
[DEBUG] helpers::signal_handler:    exiting after 2003326 microseconds
    Command being timed: "./test_signal"
    User time (seconds): 1.99
    System time (seconds): 0.00
    Percent of CPU this job got: 99%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:02.01
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 1644
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 0
    Minor (reclaiming a frame) page faults: 59
    Voluntary context switches: 1
    Involuntary context switches: 109
    Swaps: 0
    File system inputs: 0
    File system outputs: 16
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0

$ /usr/bin/time -v  ./test_signal                                                                     
[DEBUG] helpers::set_signal:    set_signal() called
[DEBUG] helpers::set_signal:    action.sa_handler: 1
[DEBUG] helpers::set_limit:     set_limit() called
[DEBUG] helpers::set_limit:     current limit: 2 seconds
i: 0    - nmsec: 12 - program has been running for 148651 microseconds
i: 1    - nmsec: 13 - program has been running for 280494 microseconds
i: 2    - nmsec: 7  - program has been running for 428390 microseconds
i: 3    - nmsec: 5  - program has been running for 580805 microseconds
i: 4    - nmsec: 10 - program has been running for 714362 microseconds
i: 5    - nmsec: 19 - program has been running for 846853 microseconds
i: 6    - nmsec: 20 - program has been running for 981253 microseconds
i: 7    - nmsec: 7  - program has been running for 1114686 microseconds
i: 8    - nmsec: 7  - program has been running for 1249530 microseconds
i: 9    - nmsec: 12 - program has been running for 1392096 microseconds
i: 10   - nmsec: 20 - program has been running for 1531859 microseconds
i: 11   - nmsec: 19 - program has been running for 1667021 microseconds
i: 12   - nmsec: 13 - program has been running for 1818431 microseconds
i: 13   - nmsec: 17 - program has been running for 1973182 microseconds
i: 14   - nmsec: 7  - program has been running for 2115423 microseconds
i: 15   - nmsec: 20 - program has been running for 2255140 microseconds
i: 16   - nmsec: 13 - program has been running for 2394162 microseconds
i: 17   - nmsec: 10 - program has been running for 2528274 microseconds
i: 18   - nmsec: 15 - program has been running for 2667978 microseconds
i: 19   - nmsec: 8  - program has been running for 2803725 microseconds
i: 20   - nmsec: 9  - program has been running for 2940610 microseconds
i: 21   - nmsec: 19 - program has been running for 3075349 microseconds
i: 22   - nmsec: 14 - program has been running for 3215255 microseconds
i: 23   - nmsec: 5  - program has been running for 3356515 microseconds
i: 24   - nmsec: 5  - program has been running for 3497369 microseconds
[DEBUG] helpers::signal_handler:    signal 24 received
[DEBUG] helpers::signal_handler:    exiting after 3503271 microseconds
    Command being timed: "./test_signal"
    User time (seconds): 3.50
    System time (seconds): 0.00
    Percent of CPU this job got: 99%
    Elapsed (wall clock) time (h:mm:ss or m:ss): 0:03.52
    Average shared text size (kbytes): 0
    Average unshared data size (kbytes): 0
    Average stack size (kbytes): 0
    Average total size (kbytes): 0
    Maximum resident set size (kbytes): 1636
    Average resident set size (kbytes): 0
    Major (requiring I/O) page faults: 0
    Minor (reclaiming a frame) page faults: 59
    Voluntary context switches: 0
    Involuntary context switches: 106
    Swaps: 0
    File system inputs: 0
    File system outputs: 16
    Socket messages sent: 0
    Socket messages received: 0
    Signals delivered: 0
    Page size (bytes): 4096
    Exit status: 0