C语言系统资源控制（getrlimit && setrlimit)

今天药忘吃喽~ 2022-09-30 04:55 167阅读 0赞

每一个进程都有自己的一组资源限制，在(\*)inux系统中我们可以通过  
\#include <sys/resource.h>  
int getrlimit(int resource, struct rlimit \*rlim);  
int setrlimit(int resource, const struct rlimit \*rlim);  
这2个API来取得和设置资源  
getrlimit用来取得setrlimit用来设置 这二个参数都需要一个要控制的资源 比如控制CPU、内存、文件描述符个数等等的控制，作为第一个参数传入，第二个参数是一个rlimit的结构体地址（指针），他的结构如下定义：  
定义放在头文件/usr/include/bits/resource.h中  
struct rlimit  
\{  
/\* The current (soft) limit. \*/  
rlim\_t rlim\_cur;  
/\* The hard limit. \*/  
rlim\_t rlim\_max;  
\};  
结构体中 rlim\_cur是要取得或设置的资源软限制的值，rlim\_max是硬限制  
这两个值的设置有一个小的约束：  
1） 任何进程可以将软限制改为小于或等于硬限制  
2） 任何进程都可以将硬限制降低，但普通用户降低了就无法提高，该值必须等于或大于软限制  
3） 只有超级用户可以提高硬限制  
一个无限的限制由常量RLIM\_INFINITY指定（The value RLIM\_INFINITY denotes no limit on a resource ）  
  
**RLIMIT\_AS**  
The maximum size of the process鈙 virtual memory (address  
space) in bytes. This limit affects calls to brk(2), mmap(2)  
and mremap(2), which fail with the error ENOMEM upon exceeding  
this limit. Also automatic stack expansion will fail (and gen-  
erate a SIGSEGV that kills the process when no alternate stack  
has been made available). Since the value is a long, on  
machines with a 32-bit long either this limit is at most 2 GiB,  
or this resource is unlimited.  
**RLIMIT\_CORE**  
Maximum size of core file. When 0 no core dump files are cre-  
ated. When nonzero, larger dumps are truncated to this size.  
**设定最大的core文件，当值为0时将禁止core文件非0时将设定产生的最大core文件大小为设定的值  
RLIMIT\_CPU**  
 CPU time limit in seconds. When the process reaches the soft  
limit, it is sent a SIGXCPU signal. The default action for  
this signal is to terminate the process. However, the signal  
can be caught, and the handler can return control to the main  
program. If the process continues to consume CPU time, it will  
be sent SIGXCPU once per second until the hard limit is  
reached, at which time it is sent SIGKILL. (This latter point  
describes Linux 2.2 and 2.4 behaviour. Implementations vary in  
how they treat processes which continue to consume CPU time  
after reaching the soft limit. Portable applications that need  
to catch this signal should perform an orderly termination upon  
first receipt of SIGXCPU.)  
**CPU时间的最大量值（秒），当超过此软限制时向该进程发送SIGXCPU信号  
RLIMIT\_DATA**  
The maximum size of the process鈙 data segment (initialized  
data, uninitialized data, and heap). This limit affects calls  
to brk() and sbrk(), which fail with the error ENOMEM upon  
encountering the soft limit of this resource.  
**数据段的最大字节长度  
RLIMIT\_FSIZE**  
 The maximum size of files that the process may create.  
Attempts to extend a file beyond this limit result in delivery  
of a SIGXFSZ signal. By default, this signal terminates a pro-  
cess, but a process can catch this signal instead, in which  
case the relevant system call (e.g., write(), truncate()) fails  
with the error EFBIG.  
**可以创建的文件的最大字节长度，当超过此软限制时向进程发送SIGXFSZ  
RLIMIT\_MEMLOCK**  
The maximum number of bytes of virtual memory that may be  
locked into RAM using mlock() and mlockall().  
**RLIMIT\_NOFILE**  
Specifies a value one greater than the maximum file descriptor  
number that can be opened by this process. Attempts (open(),  
pipe(), dup(), etc.) to exceed this limit yield the error  
EMFILE.  
**每个进程能够打开的最多文件数。更改此限制将影响到sysconf函数在参数\_SC\_CHILD\_MAX中的返回值  
RLIMIT\_OFILE is the BSD name for RLIMIT\_NOFILE.  
这里BSD系统中RLIMIT\_NOFILE的别名  
RLIMIT\_NPROC**  
The maximum number of processes that can be created for the  
real user ID of the calling process. Upon encountering this  
limit, fork() fails with the error EAGAIN.  
**每个实际用户ID所拥有的最大子进程数，更改此限制将影响到sysconf函数在参数\_SC\_CHILD\_MAX中返回的值  
RLIMIT\_RSS**  
Specifies the limit (in pages) of the process鈙 resident set  
(the number of virtual pages resident in RAM). This limit only  
has effect in Linux 2.4 onwatrds, and there only affects calls  
to madvise() specifying MADVISE\_WILLNEED.  
**最大驻内存集字节长度(RSS)如果物理存储器供不应求则内核将从进程处取回超过RSS的部份  
RLIMIT\_STACK**  
The maximum size of the process stack, in bytes. Upon reaching  
this limit, a SIGSEGV signal is generated. To handle this sig-  
nal, a process must employ an alternate signal stack (sigalt-  
stack(2)).  
**栈的最大长度  
RLIMIT——VMEM 可映照地址空间的最大字节长茺，这影响到mmap函数**  
这些限制影响到调用进程并由子进程继承！ 可以在SHELL中预设这些值ulimit命令设置  
  
小试牛刀（代码只是演示，并没有作错误处理）  
\#include <stdlib.h>  
\#include <stdio.h>  
\#include <sys/types.h>  
\#include <sys/stat.h>  
\#include <fcntl.h>  
\#include <unistd.h>  
\#include <sys/resource.h>  
int main(void)  
\{  
struct rlimit r;  
if(getrlimit(RLIMIT\_NOFILE,&r)<0)  
\{  
fprintf(stderr,"getrlimit error/n");  
exit(1);  
\}  
printf("RLIMIT\_NOFILE cur:%d/n",r.rlim\_cur);  
printf("RLIMIT\_NOFILE max:%d/n",r.rlim\_max);

/\*\* set limit \*\*/  
r.rlim\_cur=100;  
r.rlim\_max=200;  
if (setrlimit(RLIMIT\_NOFILE,&r)<0)  
\{  
fprintf(stderr,"setrlimit error/n");  
exit(1);  
\}

/\*\* get value of set \*\*/  
if(getrlimit(RLIMIT\_NOFILE,&r)<0)  
\{  
fprintf(stderr,"getrlimit error/n");  
exit(1);  
\}  
printf("RLIMIT\_NOFILE cur:%d/n",r.rlim\_cur);  
printf("RLIMIT\_NOFILE max:%d/n",r.rlim\_max);  
return 0;  
\}  
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:!gcc test.c

:!./a.out  
RLIMIT\_NOFILE cur:1024  
RLIMIT\_NOFILE max:1024  
RLIMIT\_NOFILE cur:100  
RLIMIT\_NOFILE max:200

原帖出自 [http://hi.baidu.com/phps/blog/item/7e3ba44410cf9580b3b7dc81.html][http_hi.baidu.com_phps_blog_item_7e3ba44410cf9580b3b7dc81.html]

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