lxcfs: 根据 cgroup 信息生成容器内的 /proc（下）
目录
说明
这篇笔记记录了There is no cpuacct.usage_all file in CentOS 7.2，should use cpuacct.usage_percpu ?的解决方法。这个问题最早在Lxcfs是什么？怎样通过lxcfs在容器内显示容器的CPU、内存状态中记录。
问题描述
aither64对/proc/stat的修正中使用的cgroup文件接口是cpuacct.usage_all，但是CentOS7.2中没有这个接口文件，因此没正确生成容器的CPU资源使用情况，而是直接返回了host的/proc/stat中的数据，导致在容器内看到的cpu使用率还是host的cpu使用率。
启动一个容器，只运行一个sh：
docker run -it --rm -m 256m --cpus 2 --cpuset-cpus "1,2" \
-v /var/lib/lxcfs/proc/cpuinfo:/proc/cpuinfo:rw \
-v /var/lib/lxcfs/proc/meminfo:/proc/meminfo:rw \
-v /var/lib/lxcfs/proc/stat:/proc/stat:rw \
-v /var/lib/lxcfs/proc/swaps:/proc/swaps:rw \
-v /var/lib/lxcfs/proc/uptime:/proc/uptime:rw \
centos:latest /bin/sh
什么都没做，用top命令看到的cpu使用率：
top - 04:09:52 up 0 min, 0 users, load average: 2.26, 2.65, 2.12
Tasks: 2 total, 1 running, 1 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.0 us, 0.0 sy, 0.0 ni, 99.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.3 st
%Cpu1 : 39.0 us, 61.0 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 262144 total, 260032 free, 2112 used, 0 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 260032 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 11816 1684 1348 S 0.0 0.6 0:00.04 sh
6 root 20 0 56204 2036 1468 R 0.0 0.8 0:00.00 top
解决方法
找不到cpuacct.usage_all的时候用cpuacct.usage_percpu中的信息替代，这个文件的内容格式和含义见cpuacct。实现代码，git diff d8addb023a0e bindings.c结果如下：
diff --git a/bindings.c b/bindings.c
index 049418c..9802eb6 100644
--- a/bindings.c
+++ b/bindings.c
@@ -4046,6 +4046,47 @@ static uint64_t get_reaper_age(pid_t pid)
return procage;
}
+/*
+ * Returns 0 on success.
+ * Just an implement of read_cpuacct_usage_all.
+ */
+static inline int read_cpuacct_usage_all_percpu(char *cg, char *cpuset, struct cpuacct_usage *cpu_usage, int cpucount, long ticks_per_sec)
+{
+ char *usage_str = NULL;
+ char *delim = " ";
+ char *token = NULL;
+ int j = 0;
+ uint64_t usage;
+ int rv;
+
+ if (!cpu_usage) {
+ return -1;
+ }
+
+ if (!cgfs_get_value("cpuacct", cg, "cpuacct.usage_percpu", &usage_str)) {
+ rv = -1;
+ goto err;
+ }
+
+ // usage_str formt: 120190269376599 151483821809073 145465919648605 14450503259981
+ token = strtok(usage_str, delim);
+ while (NULL != token && j < cpucount) {
+ sscanf(token,"%lu", &usage);
+ cpu_usage[j].user = usage / 1000.0 / 1000 / 1000 * ticks_per_sec;
+ cpu_usage[j].system = 0;
+ token = strtok(NULL, delim);
+ j++;
+ }
+
+ rv = 0;
+
+err:
+ if (usage_str)
+ free(usage_str);
+
+ return rv;
+}
+ /*
* Returns 0 on success.
* It is the caller's responsibility to free `return_usage`, unless this
@@ -4072,12 +4113,17 @@ static int read_cpuacct_usage_all(char *cg, char *cpuset, struct cpuacct_usage *
}
cpu_usage = malloc(sizeof(struct cpuacct_usage) * cpucount);
+ bzero(cpu_usage,sizeof(struct cpuacct_usage) * cpucount);
if (!cpu_usage)
return -ENOMEM;
if (!cgfs_get_value("cpuacct", cg, "cpuacct.usage_all", &usage_str)) {
- rv = -1;
- goto err;
+ if (read_cpuacct_usage_all_percpu(cg, cpuset, cpu_usage, cpucount, ticks_per_sec) != 0 ){
+ rv = -1;
+ goto err;
+ }else{
+ goto suc;
+ }
}
if (sscanf(usage_str, "cpu user system\n%n", &read_cnt) != 0) {
@@ -4111,6 +4157,7 @@ static int read_cpuacct_usage_all(char *cg, char *cpuset, struct cpuacct_usage *
j++;
}
+suc:
rv = 0;
*return_usage = cpu_usage;
*size = cpucount;
注意：因为cpuacct.usage_percpu中的时间没有按照user和system分开，所以全算作user时间了，在容器中会看到system占比为0。
验证
在容器内只运行了sh和top的时候：
top - 04:05:08 up 0 min, 0 users, load average: 2.99, 2.68, 1.90
Tasks: 2 total, 1 running, 1 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.3 us, 0.0 sy, 0.0 ni, 99.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu1 : 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 262144 total, 260208 free, 1936 used, 0 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 260208 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 11816 1684 1348 S 0.0 0.6 0:00.03 sh
6 root 20 0 56204 2036 1468 R 0.0 0.8 0:00.06 top
在容器内运行dd if=/dev/zero of=/dev/null，将一个CPU占满后：
top - 04:07:24 up 2 min, 0 users, load average: 3.06, 2.81, 2.06
Tasks: 4 total, 2 running, 2 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu1 :100.0 us, 0.0 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 262144 total, 259596 free, 2548 used, 0 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 259596 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
12 root 20 0 4404 356 284 R 100.0 0.1 1:29.65 dd
1 root 20 0 11816 1684 1348 S 0.0 0.6 0:00.03 sh
6 root 20 0 56204 2036 1468 R 0.0 0.8 0:00.04 top
7 root 20 0 11816 1680 1348 S 0.0 0.6 0:00.02 sh
参考
