C 关于sighandler的频率
我有一个固定时间片的计时器C 关于sighandler的频率,c,multithreading,operating-system,posix,signals,C,Multithreading,Operating System,Posix,Signals,我有一个固定时间片的计时器1s,setitimer(SIGPROF,×lice,NULL)。当我用一个线程运行进程时,sighandler会在一秒钟内被调用一次。但是,如果进程中有两个或更多线程,则每秒将调用两次sighandler。为什么会这样?或者如何拥有一个固定频率的计时器,独立于运行的线程 附加了可运行代码。打印输出显示sighandler每秒调用两次…(当NUM_线程更改为1时,情况并非如此) 编辑:我已经解决了这个问题(另见@n.m.的答案)。sighandler在多处理器
1
s,setitimer(SIGPROF,×lice,NULL)代码>。当我用一个线程运行进程时,sighandler会在一秒钟内被调用一次。但是,如果进程中有两个或更多线程,则每秒将调用两次sighandler。为什么会这样?或者如何拥有一个固定频率的计时器,独立于运行的线程
附加了可运行代码。打印输出显示sighandler每秒调用两次…(当NUM_线程更改为1时,情况并非如此)
编辑:我已经解决了这个问题(另见@n.m.的答案)。sighandler在多处理器机器上运行更频繁的原因是SIGPROF是基于CPU时间而不是实时发送的。CPU时间可以大于实时时间,例如,如果CPU时间为2秒,则可能是一个进程在1秒内有两个线程同时在2个CPU上运行。您可以使用pthread\u sigmask(…)
在创建的线程中阻止SIGPROF
。事实上,建议只有一个线程处理所有信号。在创建线程后但在加入线程之前安装信号处理程序?您的CPU有多少内核?在具有20个线程的四核计算机上尝试此操作,或者禁用一个核,看看会发生什么。@Kevin重新定位sighandler安装不起作用@n、 m.机器配备2个双核处理器。使用20时不工作threads@n.m.如前所述,这与系统中处理器的数量有关。当它在4处理器(双核,每个)系统上运行时,sighandler每秒被调用4次(即使有8个线程)。令人困惑的一点是,现在总共有8个内核,为什么不每秒调用8次处理程序呢?我不知道,也许系统配置为不将其所有功能都提供给单个进程或用户。无论如何,这种特殊类型的计时器表示进程花费的cpu秒数。如果有N
cpu,进程每秒最多可花费N
cpu秒(但如果其他进程与之竞争cpu,则花费更少)。这一点很好。出于好奇,当有多个线程时,应该只有一个线程接收信号。另外,当有3个或更多线程时,处理程序以相同的速率运行。这就是我对这个节目感到困惑的地方。
#include <sys/syscall.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/time.h>//itimerval
#include <signal.h>//sigaction, SIGPROF...
#include <pthread.h>//pthread_create()/join()
#include <stdint.h>//uint32_t
#include <stdlib.h>//exit()
using namespace std;
#ifndef NUM_THREADS
#define NUM_THREADS 20
#endif
struct sigaction old_act_;
int init_timer(int which, int musec) {
struct itimerval timeslice;
timeslice.it_interval.tv_sec = musec / 1000000;
timeslice.it_interval.tv_usec = musec % 1000000;
timeslice.it_value.tv_sec = musec / 1000000;
timeslice.it_value.tv_usec = musec % 1000000;
setitimer(which, ×lice, NULL);
return 0;
}
void remove_timer(int which)
{
struct itimerval timeslice;
timeslice.it_interval.tv_sec = 0;
timeslice.it_interval.tv_usec = 0;
timeslice.it_value.tv_sec = 0;
timeslice.it_value.tv_usec = 0;
setitimer(which, ×lice, NULL);
}
void install_handler(int signo, void(*handler)(int))
{
sigset_t set;
struct sigaction act;
act.sa_handler = handler;
act.sa_flags = SA_RESTART;
sigaction(signo, &act, &old_act_);
sigemptyset(&set);
sigaddset(&set, signo);
sigprocmask(SIG_UNBLOCK, &set, NULL);
return;
}
void uninstall_handler(int signo, bool to_block_signal)
{
sigaction(signo, &old_act_, 0);
if(to_block_signal)
{
// block the signal
sigset_t set;
sigemptyset(&set);
sigaddset(&set, signo);
sigprocmask(SIG_BLOCK, &set, NULL);
}
}
void handler(int signo)
{
pid_t tid = syscall(SYS_gettid);
pid_t pid = syscall(SYS_getpid);
struct timeval now;
gettimeofday(&now, NULL);
printf("sig %d, pid %d, tid %d, time = %u.%06u\n", signo, static_cast<int>(pid), static_cast<int>(tid), static_cast<uint32_t>(now.tv_sec), static_cast<uint32_t>(now.tv_usec));
}
void * threadRun(void * threadId)
{
for(uint64_t i = 0; i < 10000000000; i++)
{
//sleep(1);
}
}
int main()
{
int tick_musec = 1000000;
init_timer(ITIMER_PROF, tick_musec);
install_handler(SIGPROF, handler);
pthread_t threads[NUM_THREADS];
long t;
for (t = 0; t < NUM_THREADS; t++) {
printf("In main: creating thread %ld\n", t);
if (pthread_create(&threads[t], NULL, threadRun, (void *) t)) {
printf("ERROR; return from pthread_create()\n");
exit(-1);
}
}
void * status;
for (t = 0; t < NUM_THREADS; t++) {
if(pthread_join(threads[t], &status)) {
printf("ERROR; return from pthread_join()\n");
exit(-1);
}
printf("Main: completed join with thread %ld having a status of %ld\n", t, (long) status);
}
remove_timer(ITIMER_PROF);
uninstall_handler(SIGPROF, true);
printf("Main: program completed. Exiting.\n");
return 0;
}
sig 27, pid 21542, tid 21544, core 6, time = 1308168237.023219
sig 27, pid 21542, tid 21544, core 6, time = 1308168237.276228
sig 27, pid 21542, tid 21549, core 6, time = 1308168237.528200
sig 27, pid 21542, tid 21545, core 7, time = 1308168237.781441
sig 27, pid 21542, tid 21551, core 6, time = 1308168238.037210
sig 27, pid 21542, tid 21554, core 6, time = 1308168238.294218
sig 27, pid 21542, tid 21551, core 6, time = 1308168238.951221
sig 27, pid 21542, tid 21546, core 0, time = 1308168239.064665
sig 27, pid 21542, tid 21561, core 1, time = 1308168239.335642
sig 27, pid 21542, tid 21558, core 1, time = 1308168240.122650
sig 27, pid 21542, tid 21555, core 6, time = 1308168240.148192
sig 27, pid 21542, tid 21556, core 1, time = 1308168240.445638
sig 27, pid 21542, tid 21543, core 7, time = 1308168240.702424
sig 27, pid 21542, tid 21559, core 1, time = 1308168240.958635
sig 27, pid 21542, tid 21555, core 6, time = 1308168241.210182
sig 27, pid 21542, tid 21550, core 7, time = 1308168241.464426
sig 27, pid 21542, tid 21553, core 0, time = 1308168241.725650
sig 27, pid 21542, tid 21555, core 6, time = 1308168241.982178
sig 27, pid 21542, tid 21547, core 7, time = 1308168242.234422
sig 27, pid 21542, tid 21560, core 0, time = 1308168242.503647
sig 27, pid 21542, tid 21546, core 0, time = 1308168242.766902
sig 27, pid 21542, tid 21550, core 7, time = 1308168243.018414
sig 27, pid 21542, tid 21552, core 0, time = 1308168243.270643
sig 27, pid 21542, tid 21550, core 7, time = 1308168243.556412