First timer here.
While doing gdb and getting prdasummary, I know to find the panicked cpu by looking at inPanic, I also find other cpu running one process which I want to find its locals.
Can I switch to a different cpu and see its registers?
Thanks,
zXi
Related
I want to calculate current cpu usage for particular application in my code. I looked up on internet and found pdh library for windows. When I tried it I am getting overall cpu usage not cpu usage for one process.
PdhAddCounter(hquery, TEXT("\\Processor(_Total)\\% Processor Time"),0,&counter);
So what I do with this line to get cpu usage for particular process? I tried replacing _Total with process name(explorer). At that time I am getting 0 cpu usage. But I checked in resource monitor that opening many windows at a time increased cpu usage upto 20%. Still in log file cpu usage is showing 0.
Can anyone help me with this?
thanks in advance.
You need to use GetProcessTimes
And unfortunately, it won't give you the "CPU usage", it will give you the amount of CPU-time since the process started. So to get CPU usage, you will need to take one sample, store that, and then take another sample a known amount of time later, and then calculate the time (and if you want to know the total usage, you'll need to add the usertime and kerneltime together, of course).
You can check this for example. Explained everything in that project. It will give memory based on process id(same way shown in task manager)
Thanks,
Darshan
What library function can I call to get mapping of processes to cores or given a process id tell me what core it's running on, it ran last time, or scheduled to run. So something like this:
core 1: 14232,42323
core 2: 42213,63434,434
core 3: 34232,34314
core 4: 42325,6353,1434,4342
core 5: 43432,64535,14345,34233
core 6: 23242,53422,4231,34242
core 7: 78789
core 8: 23423,23124,5663
I sched_getcpu returns the core number of calling process. If there was a function that given a process id, would return the core number that would be good too but I have not found one. sched_getaffinity is not useful either; It just tells you given a process what cores it can run on which is not what I'm interested in.
I don't know that you can get information about what CPU any particular process is running on, but if you look in /proc, you'll find one entry for each running process. Under that, in /proc/<pid>/cpuset you'll find information about the set of CPUs that can be used to run that process.
Your question does not have any precise answer. The scheduler can migrate a process from one processor core to another at any time (and it is actually doing that). So by the time you got the answer it may be already wrong. And a process is usually not tied to any particular core (unless its CPU affinity has been set e.g. with sched_setaffinity(2), which is unusual; see also cpuset(7) for more).
Why are you asking? Why does that matter?
You probably want to dig inside /proc, see proc(5) man page.
In other words, if the kernel does give that information, it is thru /proc/ but I guess that information is not available because it does not make any sense.
NB. The kernel will schedule processes on the various processor cores much better than you can do, so even with a warehouse, you should not care about the core running some pid.
Yes, the virtual file /proc/[pid]/stat seems to have this info: man 5 proc:
/proc/[pid]/stat
Status information about the process. This is used by ps(1). It is
defined in /usr/src/linux/fs/proc/array.c.
(...fields description...)
processor %d (since Linux 2.2.8)
CPU number last executed on.
on my dual core:
cat /proc/*/stat | awk '{printf "%-32s %d\n", $2 ":", $(NF-5)}'
(su): 0
(bash): 0
(tail): 1
(hd-audio0): 1
(chromium-browse): 0
(bash): 1
(upstart-socket-): 1
(rpcbind): 1
..though I can't say if it's pertinent and/or accurate..
I tried looking for a thread on this subject, however couldn't find one. So posting this question.
Assume, I have created couple of threads in C++ in Linux and the code is running.
Now I would like to monitor the process and the threads of the process using a shell script and do some additional processing.
Also I would need the amount of CPU and Memory being used by each thread. I know that a thread is associated to a process, however my requirement is to identify the resources utilized by this thread.
I couldn't find the exact way to identify the threads associated to a process. I tried using PS however I couldn't find any clues. Running RHEL.
From a man page of ps:
To get info about threads:
ps -eLf
ps axms
The manpage for ps might give you more clues.
In particular, it should tell you that -L shows threads, and -o %cpu,%mem will display the amount of CPU and memory being used.
Note that memory is associated with the process, not with any thread, so there is no concept of "memory used by each thread".
Apart from using Linux commands you can use Generic Memory Manager library. Here it defined ThreadingModel class.
I have written a program that captures and displays video from three video cards. For every frame I spawn a thread that compresses the frame to Jpeg and then puts it in queue for writing to disk. I also have other threads that read from these files and decodes them in their own threads. Usually this works fine, it's a pretty CPU intensive program using about 70-80 percent of all six CPU cores. But after a while the encoding suddenly slows down and the program can't handle the video fast enough and starts dropping frames. If I check the CPU utilization I can see that one core (usually core 5) is not doing much anymore.
When this happens, it doesn't matter if I quit and restart my program. CPU 5 will still have a low utilization and the program starts dropping frames immediately. Deleting all saved video doesn't have any effect either. Restarting the computer is the only thing that helps. Oh, and if I set the affinity of my program to use all but the semi-idling core, it works until the same happens to another core. Here is my setup:
AMD X6 1055T (Cool & Quiet OFF)
GA-790FX-UD5 motherboard
4Gig RAM unganged 1333Mhz'
Blackmagic Decklink DUO capture cards (x2)
Linux - Ubuntu x64 10.10 with kernel 2.6.32.29
My app uses:
libjpeg-turbo
posix threads
decklink api
Qt
Written in C/C++
All libraries linked dynamically
It seems to me like it would be some kind of problem with the way Linux schedules threads on the cores. Or is there some way my program can mess up so bad that it doesn't help to restart the program?
Thank you for reading, any and all input is welcome. I'm stuck :)
First of all, make sure it's not your program - maybe you are running into a convoluted concurrency bug, even though it's not all that likely with your program architecture and the fact that restarting the kernel helps. I've found that, usually, a good way is a post-mortem debugging. Compile with debugging symbols, kill the program with -SEGV when it is behaving strangely, and examine the core dump with gdb.
I would try to choose a core round-robin a when new frame processing thread is spawned and pin the thread to this core. Keep statistics on how long it takes for the thread to run. If this in in fact a bug in Linux scheduler - your threads will take roughly the same time to run on any core. If the core is actually busy with something else - your threads pinned to this core will get less CPU time.
I'm a little new to GDB. I'm hoping someone can help me with something that should be quite simple, I've used Google/docs but I'm just missing something.
What is the 'normal' way folks debug threaded apps with GDB? I'm using pthreads. I'm wanting to watch only one thread - the two options I see are
a) tell the debugger somehow to attach to a particular thread, such that stepping wont result in jumping threads on each context switch
b) tell the debugger to suspend/free any 'uninteresting' threads
I'd prefer to go route b) - reading the help for GDB I dont see a command for this, tips?
See documentation for set scheduler-locking on.
Beware: if you suspend other threads, and if one of them holds a lock, and if your interesting thread needs that lock at some point while stepping, you'll deadlock.
What is the 'normal' way folks debug threaded apps
You can never debug thread correctness, you can only design it in. In my experience, most of debugging of threaded apps is putting in assertions, and examining state of the world when one of the assertions is violated.
First, you need to enable comfortable for multi-threading debugger behavior with the following commands. No idea why it's disabled by default.
set target-async 1
set non-stop on
I personally put those commands into .gdbinit file. They make your every command to be applied only to the currently focused thread. Note: the thread might be running, so you have to pause it.
To see the focused thread execute the thread.
To switch to another thread append the number of the thread, e.g. thread 2.
To see all threads with their numbers issue info thread.
To apply a command to a particular thread issue something like thread apply threadnum command. E.g. thread apply 4 bt will apply backtrace command to a thread number 4. thread apply all continue continues all paused threads.
There is a small problem though — many commands needs the thread to be paused. I know a few ways of doing that:
interrupt command: interrupts the thread execution, accepts a number of a thread to pause, without an argument breaks the focused one.
Setting a breakpoint somewhere. Note that you may set a breakpoint to a particular thread, so that other threads will ignore it, like break linenum thread threadnum. E.g. break 25 thread 4.
You may also find very useful that you can set a list of commands to be executed when a breakpoint hit through the command commands — so e.g. you may quickly print interesting values, then continue execution.