Getting CPU usage of a specific process on iOS4 - ios4

I am trying to get CPU usage of various processes (cpu ticks) from a background application running on iOS4 using Apple SDK. This is done completely with users' consents so there is nothing unethical here.
I have used sysctl to get process list but the cpu ticks for the process is always returned as 0 from the device. Alternatively, I tried to look for foreground process and polling every few seconds to get application usage that way. However, there is no API/flag which indicates if a process is running in the foreground or background. I event checked for getting memory consumption of a process and to figure out if it was running in the background (memory will not fluctuate if in the background). However, the API, proc_pidinfo, is private and Apple rejected the app.
I have seen some posts related to such topics but did not get a definite answer.
I am aware sand boxing will not allow to get info on other apps (which is, btw, not true since sysctl gives PIDs, process names and start time). However, I saw an application on the appstore called MyLife by Zokem and they report such information. They are accurate to the second. I was wondering if there is a system log or DB which stores this information.
Anyone has ideas about getting the usage time of applications?

Related

Debug high CPU usage in Azure WebApp (Linux)

I have set up an Azure WebApp (Linux) to run a WordPress and an other handmade PHP app on it. All works fine but I get this weird CPU usage graph (see below).
Both apps are PHP7.0 containers.
SSHing in to the two containers and using top I see no unusual CPU hogging processes.
When I reset both apps the CPU goes back to normal and then starts to raise slowly as shown below.
The amount of HTTP requests to the apps has not relation to the CPU usage at all.
I tried to use apache2ctl to see if there are any pending requests but that seems not possible to do inside a docker container.
Anybody got an idea how to track down the cause of this?
This is the top output. The instance has 2 cores. Lots of idle time but still over 100% load and none of the processes use the CPU ...
After handling with MS Support on that issue it seems to have boiled down to the WordPress theme being to slow or inefficient. Each request took very long and hogged CPU resources. All following requests started queuing up and thus increasing the CPU load.
Why that would not show as %CPU in top I was not explained.
They proposed to use a different theme or upscale to a multi core instance.
I am unsatisfied with that solution and will monitor further and try to find the real culprit.
I had almost exactly the same CPU Percentage graph as you did, although a Node.JS app instead of PHP. Disabling Diagnostic Logs > Docker Container Logging seems to have solved the problem for me.
I do not need those logs because I am logging to application insights.
But, in your case you might need more of those logs. I have no solution for that, but I am guessing that heavier log rotation or reducing the sizes of the logs by other means might help

Issue in pm2 - It stops responding

Am facing issue in my application servers. Assume that - there are two nodes in the Load-balancer.
Suddenly one of the node from them becomes unhealthy.
When I logged in that instance. There were no logs coming in pm2.
then I check its CPU it was very high.
So please guide me how can I fix this issue. Or any way to debug it.
Check out flame graphs to see where your Node app is CPU bound.
You can also use the new debugging system in Node 6.3 (--inspect) to debug with the full power of Chrome DevTools.
PM2 has some limited protection for runaway issues like this via the max-memory-restart option. Typically, high CPU will also correlate with high memory usage and this option can be used to restart your app when it begins consuming large amounts of memory (which in your case may or may not be the correct moment but it should help).
--max-memory-restart <memory> specify max memory amount used to autorestart (in octet or use syntax like 100M)

Node.JS V8 heap growing quickly even though usage remains the same

I'm running a Node.JS web application that works fine for a few hours and then at some random point in time, the V8 heap suddenly starts growing very quickly without a reason and about 40 minutes later, this growth usually stops and the process continues running normally.
I'm monitoring this with nodetime:
What could be the cause of this? Is it a memory leak in my program or perhaps a bug in V8?
There is no way of knowing what the issue by what you provided, but there's a 99.99% chance the problem is inside / fixable in your code.
The best tools I've found for debugging memory issues with Node.js is https://github.com/bnoordhuis/node-heapdump, you can set it up to dump a certain intervals, or by default it listens to USR2 signal, so you can send kill -s USR2 to the pid of your process and get the snapshot.
Then you can use Chrome Inspector to load the heap into it's profiling tool and start inspecting.
I've generally found the issues to be around holding on to external requests too long.

Is it possible to force termination of backgrounding apps on iOS?

I've written an app which is handling videos. As we know, video processing takes a huge amount of memory while dealing with HD resolution. My App always seemed to crash. But actually I am 100% sure, that there is no memory leak in my code. Instruments is showing no leak.
At the beginning I am startin up one OpenGLES view and the video engine. For a very short time the memory consumption is high, but falling down to normal level after the initializations are done. I am always getting memory warnings during this period. Normally this is no problem. But if I have a lot of apps in suspended mode running, the App seems to be crashing. Watching into the crash log and using the debugger shows up, that I am only running out of memory.
My customers are flooding my support mail with "app is crashing" mails. But I do know, that they have too much Apps running in the background, so there is no memory left to go. I think it's bad style programing saying the customer that he has to close Background tasks before running the app.
According to this post this is a common problem.
My question is: Is it possible to tell the OS that one needs a lot of memory so the OS should terminate some suspended Apps? This memory stuff makes me crazy, because it's no bug I could fix.
No. It is not possible to affect anything outside of your sandbox without API calls. None exist for affecting other processes in the public API.
Have you tried to minimize your memory usage? In my experience once a memory warning it thrown apps can be more likely to have problems once they are in the background, even when memory usages drops.
If you are using OpenGLES and textures, if you haven't already compress your textures. What is the specific cause of your memory allocation spike?

Debugging utilities for Linux process hang issues?

I have a daemon process which does the configuration management. all the other processes should interact with this daemon for their functioning. But when I execute a large action, after few hours the daemon process is unresponsive for 2 to 3 hours. And After 2- 3 hours it is working normally.
Debugging utilities for Linux process hang issues?
How to get at what point the linux process hangs?
strace can show the last system calls and their result
lsof can show open files
the system log can be very effective when log messages are written to track progress. Allows to box the problem in smaller areas. Also correlate log messages to other messages from other systems, this often turns up interesting results
wireshark if the apps use sockets to make the wire chatter visible.
ps ax + top can show if your app is in a busy loop, i.e. running all the time, sleeping or blocked in IO, consuming CPU, using memory.
Each of these may give a little bit of information which together build up a picture of the issue.
When using gdb, it might be useful to trigger a core dump when the app is blocked. Then you have a static snapshot which you can analyze using post mortem debugging at your leisure. You can have these triggered by a script. The you quickly build up a set of snapshots which can be used to test your theories.
One option is to use gdb and use the attach command in order to attach to a running process. You will need to load a file containing the symbols of the executable in question (using the file command)
There are a number of different ways to do:
Listening on a UNIX domain socket, to handle status requests. An external application can then inquire as to whether the application is still ok. If it gets no response within some timeout period, then it can be assumed that the application being queried has deadlocked or is dead.
Periodically touching a file with a preselected path. An external application can look a the timestamp for the file, and if it is stale, then it can assume that the appliation is dead or deadlocked.
You can use the alarm syscall repeatedly, having the signal terminate the process (use sigaction accordingly). As long as you keep calling alarm (i.e. as long as your program is running) it will keep running. Once you don't, the signal will fire.
You can seamlessly restart your process as it dies with fork and waitpid as described in this answer. It does not cost any significant resources, since the OS will share the memory pages.

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