Open Source Cloud Authors: Zakia Bouachraoui, Yeshim Deniz, Elizabeth White, Pat Romanski, Liz McMillan

Related Topics: Open Source Cloud, Linux Containers

Open Source Cloud: Article

Linux Processes: Structure, Hangs and Core Dumps

Efficient and effective resolution practices

3.  In a different shell, execute:

# pstree -p


~~~~~~Saving space~~~~~


~~~~~~Saving space~~~~~

| | -kdeinit(2872)-+-bash(2874)---thread_test (3194)-+-thread_test(3195)
| | | |-thread_test(3196)
| | | |-thread_test(3197)
| | | |-thread_test(3198)
| | | |-thread_test(3199)
| | | |-thread_test(3200)
| | | |-thread_test(3201)
| | | `-thread_test(3202)

~~~~~~Saving space~~~~~

| | `-bash(3204)---pstree(3250)

~~~~~~Saving space~~~~~

4.  We can display more details with the ps command. (Note that the PIDs would have matched if we had run these examples at the same time.)

# ps -eo pid,ppid,state,comm,time,pri,size,wchan | grep test
28807 28275 S thread_test 00:00:12 18 82272 \ schedule_timeout
Display threads with -m.
# ps -emo pid,ppid,state,comm,time,pri,size,wchan | grep test
28807 28275 S thread_test 00:00:00 18 82272 \ schedule_timeout
28808 28807 R thread_test 00:00:03 14 82272 -
28809 28807 R thread_test 00:00:03 14 82272 \ ia64_leave_kernel
28810 28807 R thread_test 00:00:03 14 82272 \ ia64_leave_kernel
28811 28807 R thread_test 00:00:03 14 82272 \ ia64_leave_kernel
28812 28807 R thread_test 00:00:03 14 82272 -
28813 28807 R thread_test 00:00:02 14 82272 \ ia64_leave_kernel
28814 28807 R thread_test 00:00:02 14 82272 \ ia64_leave_kernel
28815 28807 R thread_test 00:00:03 14 82272 -

Even though some UNIX distributions have modified commands such as ps or top to display a process with all its threads by including special options such as -m or -L, HPUX has not. Therefore, the HPUX ps command only shows the HWP process and not the underlying threads that build the process. On the other hand, Solaris can display the LWP of a process by using the -L option with its ps command.

Other vendors have created their own tools for displaying threads of a process. HPUX's glance is a good example. Using the same procedures as earlier, we demonstrate multithreads in HPUX to show the main difference between UNIX threads and Linux's implementation of threads.

HPUX 11.11:
# cc -o thread_test thread_test.c -lpthread

hpux_11.11 #glance
Process Name PID PPID Pri Name ( 700% max) CPU IO Rate RSS \ Cnt
thread_test 14689 14579 233 root 698/ 588 57.3 0.0/ 0.2 \ 560kb 9

Thus, using HPUX's glance, we can see that the thread count is nine, with one thread representing the main HWP and eight additional threads that were created by the program as shown in the source. Each thread does not have its own PID as with Linux threads. In addition, Linux tools such as top do not show the threads of a process consuming CPU cycles. This can be tested by executing the thread_test program in one tty and the top program in another tty.

Identifying Process Hangs
Now that we have covered the building blocks of processes and threads, it is time to address process hangs and their potential causes. There is little hope that killing an offending process with -9 (sigkill) will lead to discovering the root cause of a process hang. Neither will rebooting the OS unless you are dealing with a stale file handle. Furthermore, these steps will not prevent these anomalies from reoccurring. However, by applying the knowledge of how processes are created and how resources are used, the root cause can be identified.

When a process appears hung, the first step toward a solution is determining certain critical information about the task. Using the ps command, start by determining the task's state, threads, priority, parent, and wait channel. In addition, identify the cumulative CPU time and the initial start time of the task. A holistic approach is needed because although a single ps command is a good start, it will not deliver all the needed information.

Let us first determine whether the process is hung because sometimes a process appears to be blocked when it actually is in the middle of a computation or non-blocking I/O. If cumulative CPU time constantly grows, the task's state will most likely be R. In this state, the process is on the run queue and does not have a wait channel. Monitor its cumulative CPU time. If the process remains in the run queue, it might be performing some calculation that takes a while. Even the fastest computers in the world take a while to calculate an infinite loop! Nevertheless, note that a process in the run state could be the normal operation of that program, an application "feature," or a driver problem.

More Stories By James Kirkland

James Kirkland is the advocate for Red Hat's initiatives and solutions for the Internet of Things(IoT) and is the architect of its three-tier strategy for IoT deployments. For the past five years, James has been focused on IoT solutions for the transportation and energy sectors. A frequent public speaker and writer on a wide range of technical topics, James is also the co-author of Linux Troubleshooting for System Administrators and Power Users (ISBN: 0131855158) published by Prentice Hall PTR. He has been working with UNIX and Linux variants over the course of 20 years in his positions at Red Hat, and in previous roles at Racemi and Hewlett-Packard.

More Stories By David Carmichael

David Carmichael works for Hewlett-Packard as a technical problem manager in Alpharetta, Georgia. He earned a bachelors degree in computer science from West Virginia University in 1987 and has been helping customers resolve their IT problems ever since. David has written articles for HP's IT Resource Center (http://itrc.hp.com) and presented at HP World 2003.

More Stories By Greg Tinker

Greg Tinker began his career while at Bellsouth in Atlanta, Georgia. Greg joined Hewlett-Packard in 1999. Greg's primary role is as a storage business recovery specialist and has participated in HP World, taught several classes in Unix/Linux and Disk Array technology, and obtained various certifications including certifications in Advanced Clusters, SAN, and Linux.

More Stories By Chris Tinker

Chris Tinker began his career in computers while working as a Unix System Administrator for Lockheed Martin in Marietta, Georgia. Chris joined Hewlett-Packard in 1999. Chris's primary role at HP is as a senior software business recovery specialist and has participated in HP World, taught several classes in Unix/Linux and Disk Array technology, and obtained various certifications including certifications in Advanced Clusters, SAN, and Linux.

Comments (1)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

IoT & Smart Cities Stories
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...
Bill Schmarzo, Tech Chair of "Big Data | Analytics" of upcoming CloudEXPO | DXWorldEXPO New York (November 12-13, 2018, New York City) today announced the outline and schedule of the track. "The track has been designed in experience/degree order," said Schmarzo. "So, that folks who attend the entire track can leave the conference with some of the skills necessary to get their work done when they get back to their offices. It actually ties back to some work that I'm doing at the University of San...
Bill Schmarzo, author of "Big Data: Understanding How Data Powers Big Business" and "Big Data MBA: Driving Business Strategies with Data Science," is responsible for setting the strategy and defining the Big Data service offerings and capabilities for EMC Global Services Big Data Practice. As the CTO for the Big Data Practice, he is responsible for working with organizations to help them identify where and how to start their big data journeys. He's written several white papers, is an avid blogge...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more busine...
If a machine can invent, does this mean the end of the patent system as we know it? The patent system, both in the US and Europe, allows companies to protect their inventions and helps foster innovation. However, Artificial Intelligence (AI) could be set to disrupt the patent system as we know it. This talk will examine how AI may change the patent landscape in the years to come. Furthermore, ways in which companies can best protect their AI related inventions will be examined from both a US and...
Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities - ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups.
Chris Matthieu is the President & CEO of Computes, inc. He brings 30 years of experience in development and launches of disruptive technologies to create new market opportunities as well as enhance enterprise product portfolios with emerging technologies. His most recent venture was Octoblu, a cross-protocol Internet of Things (IoT) mesh network platform, acquired by Citrix. Prior to co-founding Octoblu, Chris was founder of Nodester, an open-source Node.JS PaaS which was acquired by AppFog and ...
The deluge of IoT sensor data collected from connected devices and the powerful AI required to make that data actionable are giving rise to a hybrid ecosystem in which cloud, on-prem and edge processes become interweaved. Attendees will learn how emerging composable infrastructure solutions deliver the adaptive architecture needed to manage this new data reality. Machine learning algorithms can better anticipate data storms and automate resources to support surges, including fully scalable GPU-c...
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...