基本原理 1）系统CPU使用率等于两个时间点的CPU非空闲时间差除以CPU时间总量差得到的百分比，这两者可从/proc/stat文件获得。
2）系统内存使用率等于系统物理内存消耗量除以系统物理内存总量(memtotal，以KB为单位)得到的百分比，这两者可从/proc/meminfo文件获得。
3）进程CPU使用率等于进程CPU时间(pct，以jiffies为单位)除以进程运行时间(pt)得到的百分比，pct从/proc/pid/stat文件读取utime和stime字段相加即得，pt等于系统运行时间(st，以秒为单位)减去进程启动时间(pst，以jiffies为单位),st从/proc/uptime文件获得，pst从/proc/pid/stat文件读取starttime字段获得。
4）进程内存使用率等于进程驻留集大小(rss)除以系统物理内存总量(memtotal，以KB为单位)得到的百分比，rss从/proc/pid/stat读取rss字段得到，以页数为单位。
代码实现 1）基本结构和接口定义在proc_stat.h头文件内，如下所示
1
struct sys_cpu_time
2
{
3
unsigned long long user,old_user;
4 unsigned long long nice,old_nice;
5 unsigned long long sys,old_sys;
6 unsigned long long idle,old_idle;
7 unsigned long long wait,old_wait;
8 unsigned long long hirq,old_hirq;
9 unsigned long long sirq,old_sirq;
10
};
11
12struct sys_uptime
13{
14 double uptime;
15 double idle;
16};
17
18struct sys_mem_info
19{
20 unsigned long main_total;
21 unsigned long main_free;
22 unsigned long main_used;
23 unsigned long main_buffers;
24 unsigned long main_cached;
25 unsigned long swap_total;
26 unsigned long swap_free;
27 unsigned long swap_used;
28 unsigned long swap_cached;
29};
30
31struct system_stat
32{
33 sys_cpu_time ct;
34 sys_mem_info mi;
35 sys_uptime ut;
36};
37
38struct process_stat
39{
40 char name[16];
41 char state;
42 int ppid;
43 int pgrp;
44 int session;
45 int tty_nr;
46 int tpgid;
47 unsigned int flags;
48 unsigned long minflt;
49 unsigned long cminflt;
50 unsigned long majflt;
51 unsigned long cmajflt;
52 unsigned long utime;
53 unsigned long stime;
54 long cutime;
55 long cstime;
56 long priority;
57 long nice;
58 long threads;
59 long iterealvalue;
60 unsigned long long starttime;
61 unsigned long vsize;
62 long rss;
63};
64
65struct sys_mem_entry
66{
67 const char *name;
68 unsigned long *val;
69} ;
70
71static const int PROC_STAT = 0x0001;
72static const int PROC_MEM = 0x0002;
73static const int PROC_UPTIME = 0x0004;
74static const int PROC_ALL = PROC_STAT|PROC_MEM|PROC_UPTIME;
75
76bool get_system_stat(system_stat& ss,int flag);
77
78bool get_system_usage(float& cpu,float& mem);
79
80bool get_process_stat(pid_t id,process_stat& ps);
81
82bool get_process_usage(pid_t id,float& cpu,float& mem,unsigned long long& uptime); 以上sys_cpu_time、sys_mem_info和process_stat结构只是从对应文件中选取了用于计算CPU和内存使用率必须的部分字段，如果需求扩展，可以在其后添加更多的字段；sys_mem_info中的main_used和swap_used是引申字段，它们并不对应于/proc/meminfo文件。
2）实现在proc_stat.cpp文件内，如下所示
1
static const char* PROC_FILE_STAT = "/proc/stat";
2static const char* PROC_FILE_MEMINFO = "/proc/meminfo";
3static const char* PROC_FILE_UPTIME = "/proc/uptime";
4
5static int compare_sys_mem_entry(const void *a, const void *b)
6
{
7
return strcmp(static_cast<const sys_mem_entry*>(a)->name,static_cast<const sys_mem_entry*>(b)->name);
8
}
9
10inline ssize_t file2str(const char* file,char* buf,size_t len,int* pfd=NULL)
11{
12 int fd = -1;
13 if(pfd) fd = *pfd;
14
15
if(-1 == fd){
16 fd=open(file,O_RDONLY,0);
17 if(-1==fd) return -1;
18 if(pfd) *pfd = fd;
19
}else
20 lseek(fd,0,SEEK_SET);
21
22 ssize_t ret = read(fd,buf,len-1);
23 if(NULL==pfd) close(fd);
24 if(ret <= 0) return -1;
25 buf[ret] = '\0';
26
27 return ret;
28}
29
30bool get_system_stat(system_stat& ss,int flag)
31{
32 assert(flag&PROC_ALL);
33
34 char buf[2048];
35 ssize_t ret;
36
37 if(flag & PROC_STAT){
38 static __thread int stat_id = -1;
39 ret = file2str(PROC_FILE_STAT,buf,sizeof(buf),&stat_id);
40 if (-1==ret) return false;
41 sys_cpu_time* ct = &ss.ct;
42 if(7!=sscanf(buf,"cpu %Lu %Lu %Lu %Lu %Lu %Lu %Lu",&ct->user,&ct->nice,&ct->sys,&ct->idle,
43 &ct->wait,&ct->hirq,&ct->sirq))
44 return false;
45 }
46
47 if(flag & PROC_UPTIME){
48 static __thread int uptime_id = -1;
49 ret = file2str(PROC_FILE_UPTIME,buf,sizeof(buf),&uptime_id);
50 if(-1==ret) return false;
51 sys_uptime* ut = &ss.ut;
52 if(2!=sscanf(buf,"%lf %lf",&ut->uptime,&ut->idle))
53 return false;
54 }
55
56 if(flag & PROC_MEM){
57 static __thread int mem_id = -1;
58 ret = file2str(PROC_FILE_MEMINFO,buf,sizeof(buf),&mem_id);
59 if(-1==ret) return false;
60
61 sys_mem_info *mi = &ss.mi;
62 const sys_mem_entry mem_table[] = {
63 {"Buffers", &mi->main_buffers},
64 {"Cached", &mi->main_cached},
65 {"MemFree", &mi->main_free},
66 {"MemTotal", &mi->main_total},
67 {"SwapCached", &mi->swap_cached},
68 {"SwapFree", &mi->swap_free},
69 {"SwapTotal", &mi->swap_total}
70 };
71
72 char *beg,*end = buf + ret;
73 char *colon,*lf;
74 sys_mem_entry key,*sme;
75
76 for(beg=buf;beg<end;beg=lf+1){
77 colon = strchr(beg,':');
78 if(!colon) break;
79 *colon++ = '\0';
80 lf = strchr(colon,'\n');
81 if(!lf) break;
82 key.name = beg;
83 sme = (sys_mem_entry*)bsearch(&key,mem_table,NUM_ELEMENTS(mem_table),sizeof(sys_mem_entry),compare_sys_mem_entry);
84 if(sme) *(sme->val) = ::strtoul(beg=colon,&colon,10);
85 }
86 mi->main_used = mi->main_total - mi->main_free;
87 mi->swap_used = mi->swap_total - mi->swap_free;
88 }
89
90 return true;
91}
92
93bool get_system_usage(float& cpu,float& mem)
94{
95 static __thread system_stat ss = {0};
96 if(!get_system_stat(ss,PROC_MEM|PROC_STAT))
97 return false;
98
99 sys_cpu_time* ct = &ss.ct;
100 long long user,nice,sys,idle,wait,hirq,sirq,sum;
101 user = ct->user - ct->old_user;
102 nice = ct->nice - ct->old_nice;
103 sys = ct->sys - ct->old_sys;
104 idle = ct->idle - ct->old_idle;
105 if(idle<0) idle = 0;
106 wait = ct->wait - ct->old_wait;
107 hirq = ct->hirq - ct->old_hirq;
108 sirq = ct->sirq - ct->old_sirq;
109 ct->old_user = ct->user;
110 ct->old_nice = ct->nice;
111 ct->old_sys = ct->sys;
112 ct->old_idle = ct->idle;
113 ct->old_wait = ct->wait;
114 ct->old_hirq = ct->hirq;
115 ct->old_sirq = ct->sirq;
116
117 sum = user + nice + sys + idle + wait + hirq + sirq;
118 if(sum<1) sum = 1;
119 cpu = 100.0*(sum - idle)/sum;
120
121 sys_mem_info* mi = &ss.mi;
122 mem = 100.0*mi->main_used/mi->main_total;
123
124 return true;
125}
126
127bool get_process_stat(pid_t id,process_stat& ps)
128{
129 char buf[1024],name[64];
130
131 sprintf(name,"/proc/%u/stat",id);
132 ssize_t ret = file2str(name,buf,sizeof(buf));
133 if(-1==ret) return false;
134
135 char* beg = strchr(buf,'(');
136 if(!beg) return false;
137
138 char* end = strchr(++beg,')');
139 if(!end) return false;
140
141 size_t num = end - beg;
142 if(num >= sizeof(name))
143 num = sizeof(name) -1;
144 memcpy(ps.name,beg,num);
145 ps.name[num] = '\0';
146
147 return 22/**//*1+5+1+6+6+1+1+1*/ == sscanf(end+2,
148 "%c "
149 "%d %d %d %d %d "
150 "%u "
151 "%lu %lu %lu %lu %lu %lu "
152 "%ld %ld %ld %ld %ld %ld "
153 "%Lu "
154 "%lu "
155 "%ld",
156 &ps.state, //1
157 &ps.ppid,&ps.pgrp,&ps.session,&ps.tty_nr,&ps.tpgid, //5
158 &ps.flags,//1
159 &ps.minflt,&ps.cminflt,&ps.majflt,&ps.cmajflt,&ps.utime,&ps.stime,//6
160 &ps.cutime,&ps.cstime,&ps.priority,&ps.nice,&ps.threads,&ps.iterealvalue, //6
161 &ps.starttime,//1
162 &ps.vsize,//1
163 &ps.rss); //1
164}
165
166bool get_process_usage(pid_t id,float& cpu,float& mem,unsigned long long& uptime)
167{
168 system_stat ss;
169 if(!get_system_stat(ss,PROC_MEM|PROC_UPTIME))
170 return false;
171
172 process_stat ps;
173 if(!get_process_stat(id,ps))
174 return false;
175
176 long HZ = sysconf(_SC_CLK_TCK);
177 unsigned long long pct = ps.utime+ps.stime;
178 uptime = (unsigned long long)ss.ut.uptime - ps.starttime/HZ;
179 cpu = uptime ? (100.0*pct/HZ)/uptime : 0.0;
180
181 long page_size = sysconf(_SC_PAGESIZE) >> 10;
182 mem = 100.0*ps.rss*page_size/ss.mi.main_total;
183
184 return true;
185} 以上get_system_stat接口的实现中，sys_mem_entry数组mem_table中的元素对应于sys_mem_info中的字段，并按其名称升序排列，便于二分查找。如果需求扩展改变了sys_mem_info结构的成员，只须调整mem_table，保证元素按字段名称升序排列即可。
性能优化
如果频繁调用get_xxx_usage来获得资源使用信息，那么存在着不断打开和关闭描述符操作，而在某些情况下没必要，例如读取一些系统proc文件如/proc/stat、/proc/meminfo和/proc/uptime等，只需第一次调用时打开，后续直接读数据即可，这样更高效。所以file2str的实现，支持一次打开，多次读取，当进程退出时，系统内核会自动关闭所有描述符。
posted on 2013-05-31 19:04
春秋十二月 阅读(4925)
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