I have done some searching around the internet and this site, but I haven't found a good way to count the context switches on a thread in a c++ program I am running. I need to know if it get swapped off of a CPU for correct timing.
View 4 RepliesAs a part of a school project I am working on monitoring context switches. I'm working on redhat 8.0, kernel version 2.4.18-14 and for some reason I keep getting unclassified reasons which causing context switches from a process to itself. I am trying to determine each context switch, what was the reason that causes it, whether time slice ended, or yielded, or went for waiting or returned from waiting or parameters changed or task ended to task forked or any possible reason.
But all the time I find that the only switches that I cannot determine the reason happens from a process to itself, all this unrecognized switches from process to itself happens only on interactive processes, and sometimes the need_resched flag is on and sometimes is off. What could possibly cause a context switch from a process to itself? Can a returning of a process with a lower (higher by number) priority from waiting cause a context switch?
I have a user complaining about performance:-
Quote: At times on our server, during more-or-less idle moments, context switching is around the 2000-3000 mark.When we run the app, we can get this up to the 500,000 CSs per second. Not only this, but at the same time, the CPUs go to >60% system (the kernel is having to do all that context switching after all), leaving only around 30% for user space. We think it is a possibility that the massive context switching is contributing significantly to our performance issues.
The server is a HP DL580 G5 with 4 x Intel Xeon E7340 @ 2.4Ghz.My issue is that I don't know if the contect switching is a problem or not.From what i've read those values are not necesserilly cause for concern.
I am going to use "pthread_setaffinity_np" to bind a thread to a specific core. My application has two threads. I have used mutex to assign a specific id to each thread and then bind that thread to a core different from another core. but it seems that the os assigns both thread to one core.What should I do to bind each thread to a specific core?
View 4 Replies View RelatedI am loading variables for cXtXdXsX disk names into a script, and at present I have only accounted for there being 3 characters from c to t. I need to change it to a variable recognition so that it can count any number of charcters such as c1t , c10t , or c100t.
I can then take that information and use it with the following string to strip off the lead characters so as to make the 3 in $substr either a variable or redirect to multiple occurrences of raw based on the count returned.
sub raw {
$substr = substr ($_, 3);
$raw1 = substr ($substr, 0, -4);
$raw = lc($raw1);
}
how to count from the c to the t inclusive so I get 3, 4, 5, etc ...
If I read in variables entered by the user, how can I check to make sure the correct number of variables were entered? For example, after reading in a data file and making it into an array, I have:echo "To check the data, enter the first element number, last element number and step size as x y z:"read x y z.It then goes on to start a loop, but what I would like now (before the loop) is a check to see if three variables have been entered, before the rest of the script continues.
I've tried specifying the variables as $1, $2 and $3, but if I echo $#, the value comes out as zero, so it's obviously not working.
Is there a way to count the number of errors- an exit variable $? from one function?
The output from the exit variable (either erroneous or correct (1) or (0)) is it possible to add the erroneous one ups?
So this is my code:
Code:
Modification of code I found here. It works, but I don't really know why.
Q1: Why is each filter hit counted only when the conditional is not true?
Q2: I've tried taking the file type, (.old), and put it into a variable for better usability, but then the script fails.
A simple TCP based chat server could allow users to use any TCP client (telnet, for example) to communicate with each other. For this question you should consider a single process, single thread server that can support exactly 2 clients at once, the server simply forwards whatever is sent from one client to the other (in both directions). Your server must not insist on any specific ordering of messages as soon as something is sent from one client it is immediately forwarded to the other client. As soon as either client terminates the connection the server can exit
View 4 Replies View RelatedI have a coredump file which gives stacktrace. But I dont know which thread executed or any task switches happened before a crash happened from a given thread. is there anyway to find out.
View 3 Replies View RelatedI had been working on a CPP code for sometime now, without being aware that some parts of its code, especially security related were not being compiled. Problem was like my product did not work for SSL mode. On analysis, I found that some part of CPP codes inside a switch(ENABLE_SSL_LIBRARY)were not getting compiled at all. And also that this gets set when we do newgrp crypto command on the box. This left me without lots of doubts. I wanted to understand how these switches work and if this switch was propreitary to my code or something related to Linux.
My questions now are:
1. Switches like the one mentioned above, are they user defined, for my particular code or are they related to Linux/GCC or makefiles?
2.If a user can define such switches to control code compilation, then need to know the concepts/procedures behind it. How is it done ?
Kindly excuse if these are very very basic. But since I could not get proper stuffs on google, I thought I should ask some experts here who could either explain me or point me to appropriate resources (links of articles / tutorials)
I want to allow my program to be able to run in DEBUG mode. i.e., I want to be able to run ./program, and I want to be able to run ./program -v to show all the debug output. How do I go about setting up something like that?
View 3 Replies View RelatedWhat is the quickest way to get the thread id(tid) of the current thread in linux? Specifically I use fedora 13. ...and I am talking about inside a C++ program.
View 2 Replies View RelatedIs there a library/system call that will return to me what CPU core a thread of execution is running on? I've looked for a bit on the net already and also in /usr/include and couldn't find one.
getcpu() and sched_getcpu() are two that I found, but when I include the appropriate header files (linux/getcpu.h, and sys/sched.h respectively), gcc says getcpu.h doesn't exist and the linker complains it cannot find the implementation in sched.h.
I'm sure I'm doing something really stupid or overthinking...
What I am doing is running an OpenMP application and specifying a list of cpu cores to run on with GOMP_CPU_AFFINITY. I want to make sure that each core is getting the same number of threads.
**UPDATE**
It seems that this code works, but only with glibc >= 2.6, and my machine has 2.5:
Code:
#define _GNU_SOURCE
#include <stdio.h>
#include <utmpx.h>
int main( void )
[Code].....
I am using multi threading programming. In this from one of the thread I am calling other module's function with function pointer as argument. When that module calls the callback function in which context the function runs(thread/process). As per my observation it looks like running in process context (main process).
View 1 Replies View RelatedI have a program which is uses sigaction to register for a SIGIO signal (for incoming data on a fd) with an appropriate event handler. I also create a new detached thread 'B' that does some work with the received data. Normally the thread B runs properly. But when my event handler is called (because a there is new incoming data), after the event is handled, the thread B is not called immediately. There is a noticeable delay of the order of many seconds before it is scheduled again .During this delay, my program is doing nothing.
What am i doing wrong? Is there someway i can run thread B as soon as the event is handled (and assuming no other work is to be carried out)?
i created one thread in main(). I have while in thread function.
I want close the thread in main after some time. How can i close it.
Kernel: 2.6.24.2
System: Embedded System
I have a process and two threads running in it. Thread1 is my GUI-Thread (using FLTK) and Thread2 is running at the first 10 sec. after start.Now, I would like to make Thread2 "nicer" to Thread1, because otherwise GUI stucks sometimes. But I didn't find a solution.Is it possible to define the "niceness" of threads inside a process (to each other)? And if so, how do I have to do this?
I have to launch a new thread from my existing main program and pass data to it.
For now the data is simply a string value.
How I go about passing data to a new thread while it is running.
When I set the stack base address of the child thread using the POSIX library function "pthread_attr_setstackaddr()", I am unable to access the memory contents of its parent. The data-structures that are created on the HEAP of its parent using malloc() are either getting destroyed or unaccessible when moving to the context of the child thread. These data-structures are being passed as an argument to the child thread.Even if I make these variables global then also it is not working.pthread_attr_setstacksize(tattr, ...);stackbase = (void *) malloc(...);pthread_attr_setstackaddr(tattr, stackbase);But when I create the child thread without setting its stack base address using that pthread_attr_setstackaddr(), then it is able to access the parent's memory contents.
View 1 Replies View RelatedI've been playing around a bit with Xlib programming, and I'm just wondering if anyone knows of a good tutorial involving XContext's? Even if someone could explain the concept to me a bit.
View 1 Replies View RelatedHow to get list of threads of a process using C code in Linux?
View 6 Replies View RelatedI have a timer thread, and when it expires, it sets a flag. The only problem is, if any higher priority thread comes in between, then the timer is not expired in real time.Thus i want to set a highest priority to my thread. Now, i know 2 algos, which can make my thread in real time are: SCHED_FIFO and SCHED_RR.
So, here are my queries: 1) Which scheduling algo is best suited for this purpose? 2) Is it guaranted to work in real time if i use that algo (you suggest in 1) and set the max_priority by getting the maximum settable priority for that particular algorithm using, int sched_get_priority_max(int policy);
I have created an error logger thread in my application using pthread_create(), I want this thread to have a lower priority than my application's priority so that the application would run properly. Is there an easy way to do this? I know that we can change priority for thread created with policies FIFO or RR, since I don't set the policy for my application, I don't know what to set for my thread.
View 4 Replies View RelatedI want to suspend/resume a thread. The library I am using is pthread.h.I am also running my application on linux.Is there any function in pthread. let me suspend a thread temporary?I have read a document in which it was mentioned thatthread does not support suspend/resume
View 4 Replies View RelatedI seem to only be able to set my stack size on my linux server to 15000. If I increase it to 20000 I get a Segmentation Fault. how I can get the linux OS to increase the stack size? Code: threadRet |= pthread_attr_setstacksize( &m_ThreadAttributes, 15000 );
View 8 Replies View RelatedI don't seem to find a conclusive answer to this one...."Is popen thread safe via pthreads?"
View 2 Replies View RelatedI am new to thread programming. I need to generate one thread in one process using posix thread. Which scheduling and priority do i need to use? I want to generate the thread with the lowest priority. As i know there are 3 scheduling policy available SCHED_FIFO, SCHED_RR or SCHED_OTHAR.
View 1 Replies View RelatedThis is a client server issue where the server creates a new thread for listening to a new client, now when the thread starts execution and during its execution the server needs to pass it an object of some X class, how's that to be done?
View 4 Replies View RelatedI am trying to pass an array to thread program. Its printing the val[0] value but its not printing value at val[1]. Can somebody help me with this problem.
Code:
#include <unistd.h>
#include <stdlib.h>
[code]....