Question

我编写了一个程序，用于监视子进程的资源。我使用wait4函数的第四个参数来获取子进程的CPU使用率，这很好。但我可以用它来获取内存，它看起来与“ps”的输出不同。我也尝试解析/ proc / pid / status，但有时它不准确，因为某些子进程太快无法解析。谁能给我一些建议或解决方案？非常感谢。

Answer 1

一旦进程终止，即使进程条目仍然存在于内核中，内核也会释放该进程的所有资源。所以，我不希望能够从/ proc。

读取进程的内存大小

此外，该过程没有“使用的最大内存”统计信息。

我可以考虑确定进程的最大内存量的唯一方法如下：

在执行过程中定期对进程状态进行采样并获取当前内存使用情况，
使用strace捕获进程发出的所有系统调用并对其进行处理，以确定进程使用了多少内存，或者
使用共享库拦截进程创建的内存分配系统调用，捕获详细信息并找到报告方式

除非绝对需要非常高的准确度，否则我可能会选择（1）。

可能有分析或统计工具来帮助完成此任务，但我不知道。

使用Strace

这是一个程序，用于说明strace用于此目的：

<强> allocit.c

#include <stdio.h>
#include <stdlib.h>

int main ()
{
        int     cur;

        cur = 0;
        while ( cur < 1000 )
        {
                malloc(1024);
                cur++;
        }

        return  0;
}

使用strace（strace ./allocit）运行此输出会得到如下输出：

execve("./allocit", ["./allocit"], [/* 49 vars */]) = 0
brk(0)                                  = 0x1b991000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ae49dccd000
uname({sys="Linux", node="fearless.office.tmcs", ...}) = 0
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/home/jdoe/lib/tls/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/home/jdoe/lib/tls/x86_64", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/home/jdoe/lib/tls/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/home/jdoe/lib/tls", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/home/jdoe/lib/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/home/jdoe/lib/x86_64", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/home/jdoe/lib/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/home/jdoe/lib", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/software/ticketmaster/lib/tls/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/software/ticketmaster/lib/tls/x86_64", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/software/ticketmaster/lib/tls/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/software/ticketmaster/lib/tls", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/software/ticketmaster/lib/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/software/ticketmaster/lib/x86_64", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/software/ticketmaster/lib/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/software/ticketmaster/lib", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/usr/lib/oracle/11.2/client64/lib/tls/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib/oracle/11.2/client64/lib/tls/x86_64", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/usr/lib/oracle/11.2/client64/lib/tls/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib/oracle/11.2/client64/lib/tls", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/usr/lib/oracle/11.2/client64/lib/x86_64/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib/oracle/11.2/client64/lib/x86_64", 0x7fff896b2900) = -1 ENOENT (No such file or directory)
open("/usr/lib/oracle/11.2/client64/lib/libc.so.6", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib/oracle/11.2/client64/lib", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=123338, ...}) = 0
mmap(NULL, 123338, PROT_READ, MAP_PRIVATE, 3, 0) = 0x2ae49dcce000
close(3)                                = 0
open("/lib64/libc.so.6", O_RDONLY)      = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\220\332!\2359\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1717800, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ae49dced000
mmap(0x399d200000, 3498328, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x399d200000
mprotect(0x399d34e000, 2093056, PROT_NONE) = 0
mmap(0x399d54d000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x14d000) = 0x399d54d000
mmap(0x399d552000, 16728, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x399d552000
close(3)                                = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x2ae49dcee000
arch_prctl(ARCH_SET_FS, 0x2ae49dcee210) = 0
mprotect(0x399d54d000, 16384, PROT_READ) = 0
mprotect(0x399d01b000, 4096, PROT_READ) = 0
munmap(0x2ae49dcce000, 123338)          = 0
brk(0)                                  = 0x1b991000
brk(0x1b9b2000)                         = 0x1b9b2000
brk(0x1b9d3000)                         = 0x1b9d3000
brk(0x1b9f4000)                         = 0x1b9f4000
brk(0x1ba15000)                         = 0x1ba15000
brk(0x1ba36000)                         = 0x1ba36000
brk(0x1ba57000)                         = 0x1ba57000
brk(0x1ba78000)                         = 0x1ba78000
brk(0x1ba99000)                         = 0x1ba99000
exit_group(0)                           = ?

注意用于扩展堆的所有brk()调用。

如何准确地执行子进程后的最大内存使用量？

1 个答案:

使用Strace