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Accelerated Linux Core Dump Analysis

Identify Spiking Threads

Learn how to identify spiking threads.

We'll cover the following...

What’s a spiking thread?

We refer to a thread that causes a sudden rise in CPU usage as a spiking thread (as it spikes the CPU). This usually happens due to some sort of infinite loop. In this exercise, we’ll learn how to identify spiking threads from the core dump.

Application source code

We have created a multi-threaded application that generates a spiking thread.

C++ 17
// Build:
// gcc main.c -pthread -lm -static -o App3
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
void procA()
{
    while (1)
    {    
        sleep(1);
    }
}
void procB()
{
    double d = 1.0/3.0;
    while (1)
    {   
        d = sqrt(d);
    }
}
#define THREAD_DECLARE(num,func) void bar_##num() \
{ \
    func; \
} \
\
void foo_##num() \
{ \
    bar_##num(); \
} \
\
void * thread_##num (void *arg) \
{ \
    foo_##num(); \
    \
    return 0; \
}
THREAD_DECLARE(one,sleep(-1))
THREAD_DECLARE(two,sleep(-1))
THREAD_DECLARE(three,procA())
THREAD_DECLARE(four,sleep(-1))
THREAD_DECLARE(five,procB())
#define THREAD_CREATE(num) {pthread_t threadID_##num; pthread_create (&threadID_##num, NULL, thread_##num, NULL);}
int main(int argc, const char * argv[])
{
    THREAD_CREATE(one)
    THREAD_CREATE(two)
    THREAD_CREATE(three)
    THREAD_CREATE(four)
    THREAD_CREATE(five)    
    
    sleep(-1);
    return 0;
}

If we were to run this application and observe the CPU usage using the top command, we’d observe that it’s ...