在/proc/stat中报告的Android cpu内核 [英] Android cpu cores reported in /proc/stat
问题描述
我正在开发一个Android应用程序，该应用程序显示每个内核的CPU负载和内存消耗.对于CPU负载，我正在读取/proc/stat，对于内存->/proc/meminfo. 但是，我看到/proc/stat中的CPU内核数在随后的文件读取过程中发生了变化.
I am developing an Android application that shows the CPU load per core and memory consumption. For CPU load I am reading /proc/stat and for memory -> /proc/meminfo. However I see that the number of CPU cores in /proc/stat is changing during subsequent reading of the file.
cpu 230599 10622 84595 1892023 8236 16 285 0 0 0
cpu0 138005 7992 58080 1738918 6407 16 278 0 0 0
intr 9136791 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9601 0 0 0 0 0 0 .......
ctxt 16904510
btime 1394641996
processes 16919
procs_running 2
procs_blocked 0
softirq 1688530 407 706934 422 1558 407 407 92978 324500 1267 559650
cpu 230599 10622 84595 1892023 8236 16 285 0 0 0
cpu0 138005 7992 58080 1738918 6407 16 278 0 0 0
intr 9136791 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9601 0 0 0 0 0 0 .......
ctxt 16904510
btime 1394641996
processes 16919
procs_running 2
procs_blocked 0
softirq 1688530 407 706934 422 1558 407 407 92978 324500 1267 559650
5秒后变为:
cpu 230772 10623 84671 1890801 8236 16 286 0 0 0
cpu0 138104 7993 58126 1739267 6407 16 279 0 0 0
cpu1 92668 2630 26545 151534 1829 0 7 0 0 0
intr 9144729 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9601 0 0 0 0 0 0 ........
ctxt 16923744
btime 1394641996
processes 16946
procs_running 2
procs_blocked 0
softirq 1690205 407 707396 422 1558 407 407 93311 324790 1267 560240
cpu 230772 10623 84671 1890801 8236 16 286 0 0 0
cpu0 138104 7993 58126 1739267 6407 16 279 0 0 0
cpu1 92668 2630 26545 151534 1829 0 7 0 0 0
intr 9144729 0 0 0 0 0 0 0 0 0 0 0 0 0 0 9601 0 0 0 0 0 0 ........
ctxt 16923744
btime 1394641996
processes 16946
procs_running 2
procs_blocked 0
softirq 1690205 407 707396 422 1558 407 407 93311 324790 1267 560240
这是否意味着在某些情况下cpu内核正在休眠?
Does it mean that cpu cores are sleeping in some cases?
推荐答案
我知道这很旧，但是似乎没有答案，我也在寻找解决方案.
I know this is old, but there does not seem to be an answer for this, and I've been searching for a solution as well.
我想出的是，如果我要记录每个跟在数字后面的名为"cpu"的核心.和cpus从0-3开始.如果我按顺序阅读内核.然后，如果/proc/stat的.readline()返回不包含cpu的字符串，则该内核一定不能工作，并且处于脱机状态.因此，从理论上讲，这将是零使用率.因此，返回0.
What I figured, is that if I'm recording each core named "cpu" that follows a number. and the cpus go from 0-3. And if I'm reading the cores in order. Then if .readline() of /proc/stat returns a string that does NOT contain cpu, than that core must not be working, and is offline. So, in theory, it would be at zero percent usage. So, return 0.
*带有代码的完整答案，请参见下文*
这里有一些代码，以防万一我说的没有意义，我的代码是基于此的: 在Android中获取内存使用情况
Heres some code, in case what I said didn't make sense, mine is based on this: Get Memory Usage in Android
这是我如何找到一种新的计算方法，可以使我更准确地表示核心读数:
and here is how I found a new calculation that gave me more accurate representation of core readings: How to get total cpu usage in Linux (c++)
首先，这是我的一些CPU函数，这些函数在这些循环和填充后显示给用户.我将其发布，以便您更好地了解i以及我的代码的含义
First, here is some of my CPU function that displays a string after these loops and stuff to the user. I'm posting this so you have a better understanding of i, and what my code means
float[] coreValues = new float[10];
//get how many cores there are from function
int numCores = getNumCores();
for(byte i = 0; i < numCores; i++)
{
coreValues[i] = readCore(i);
}
getNumCores可以在这里找到，我不会发布，因为我觉得这样做的人应该得到它的荣誉:
getNumCores can be found here, I will not be posting since I feel like the person who did should get the credit for it: How can you detect a dual-core cpu on an Android device from code?
最后，这是我的代码，希望它有意义，并且我提供了很多评论.
And, lastly, here's my code, I hope it makes sense, and I offered a lot of comments.
//for multi core value
private float readCore(int i)
{
/*
* how to calculate multicore
* this function reads the bytes from a logging file in the android system (/proc/stat for cpu values)
* then puts the line into a string
* then spilts up each individual part into an array
* then(since he know which part represents what) we are able to determine each cpu total and work
* then combine it together to get a single float for overall cpu usage
*/
try {
RandomAccessFile reader = new RandomAccessFile("/proc/stat", "r");
//skip to the line we need
for(int ii = 0; ii < i + 1; ++ii)
{
reader.readLine();
}
String load = reader.readLine();
//cores will eventually go offline, and if it does, then it is at 0% because it is not being
//used. so we need to do check if the line we got contains cpu, if not, then this core = 0
if(load.contains("cpu"))
{
String[] toks = load.split(" ");
//we are recording the work being used by the user and system(work) and the total info
//of cpu stuff (total)
//https://stackoverflow.com/questions/3017162/how-to-get-total-cpu-usage-in-linux-c/3017438#3017438
long work1 = Long.parseLong(toks[1])+ Long.parseLong(toks[2]) + Long.parseLong(toks[3]);
long total1 = Long.parseLong(toks[1])+ Long.parseLong(toks[2]) + Long.parseLong(toks[3]) +
Long.parseLong(toks[4]) + Long.parseLong(toks[5])
+ Long.parseLong(toks[6]) + Long.parseLong(toks[7]) + Long.parseLong(toks[8]);
try
{
//short sleep time = less accurate. But android devices typically don't have more than
//4 cores, and I'n my app, I run this all in a second. So, I need it a bit shorter
Thread.sleep(200);
}
catch (Exception e) {}
reader.seek(0);
//skip to the line we need
for(int ii = 0; ii < i + 1; ++ii)
{
reader.readLine();
}
load = reader.readLine();
//cores will eventually go offline, and if it does, then it is at 0% because it is not being
//used. so we need to do check if the line we got contains cpu, if not, then this core = 0%
if(load.contains("cpu"))
{
reader.close();
toks = load.split(" ");
long work2 = Long.parseLong(toks[1])+ Long.parseLong(toks[2]) + Long.parseLong(toks[3]);
long total2 = Long.parseLong(toks[1])+ Long.parseLong(toks[2]) + Long.parseLong(toks[3]) +
Long.parseLong(toks[4]) + Long.parseLong(toks[5])
+ Long.parseLong(toks[6]) + Long.parseLong(toks[7]) + Long.parseLong(toks[8]);
//here we find the change in user work and total info, and divide by one another to get our total
//seems to be accurate need to test on quad core
//https://stackoverflow.com/questions/3017162/how-to-get-total-cpu-usage-in-linux-c/3017438#3017438
return (float)(work2 - work1) / ((total2 - total1));
}
else
{
reader.close();
return 0;
}
}
else
{
reader.close();
return 0;
}
}
catch (IOException ex)
{
ex.printStackTrace();
}
return 0;
}
最后，我的readCore函数将返回0.0-1.0的值，您需要乘以100才能得到一个百分比.
And, as a last note, my readCore function will return a value of 0.0 - 1.0, you need to multiply by 100 to get a percentage.
EDIT 如以下评论所要求，Android文档:在处于活动状态时，CPU可以联机或脱机，更改时钟速度和相关电压(可能还会影响内存总线速度和其他系统核心电源状态)，并且可以进入较低的电源空闲状态在内核空闲循环中时，它们不仅处于状态状态.不仅为功率配置文件测量了这些不同的CPU功率状态，而且在测量其他参数时可能有必要避免功率消耗的差异."
EDIT As requested from the comments below, Android documentation: "While active, CPUs can be brought online or put offline, change clock speeds and associated voltages (possibly also affecting memory bus speeds and other system core power state), and can enter lower power idle states while in the kernel idle loop. Not only are these different CPU power states measured for the power profile, it may be necessary to avoid the power draw variance when measuring other parameters."
链接: https://source.android.com/devices/tech/power.html#
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