Preventing Your Programs From Overrunning Our Computers - Revision history

Steve410: /* And, Worth Mentioning Again... */

2024-10-02T20:28:18Z

And, Worth Mentioning Again...

Steve410: /* Computing System Resources that Could Be Exceeded */

2024-10-02T20:26:56Z

Computing System Resources that Could Be Exceeded

Steve410: /* Computing System Resources that Could Be Exceeded */

2024-10-02T20:26:34Z

Computing System Resources that Could Be Exceeded

Phil at 14:35, 7 June 2024

2024-06-07T14:35:32Z

Steve410: /* Modifying a Process's Running Priority */

2022-03-21T17:20:01Z

Modifying a Process's Running Priority

Steve410: /* Tips to Prevent Your Programs from Exceeding the System Resources on Our Computers */

2022-03-21T17:16:21Z

Tips to Prevent Your Programs from Exceeding the System Resources on Our Computers

Steve410 at 21:36, 1 September 2021

2021-09-01T21:36:12Z

Phil.cs.jhu.edu at 15:26, 4 December 2017

2017-12-04T15:26:14Z

Steve410.cs.jhu.edu: /* Who Is Affected When Your Program Uses Up Resources On One Of Our Linux Systems? */

2017-11-21T15:32:43Z

Who Is Affected When Your Program Uses Up Resources On One Of Our Linux Systems?

Steve410.cs.jhu.edu: /* Modifying A Process Running Priority */

2017-11-20T18:22:11Z

Modifying A Process Running Priority

@@ Line 103: / Line 103: @@
 ==And, Worth Mentioning Again...==
-: Please remember that because these are multiuser systems,  ''other users could be logged into the system and could be affected if your running program exceeds the computer's resources.''
+: Please remember that because these are '''multiuser''' systems,  ''other users could be logged into the system and could be affected if your running program exceeds the computer's resources.''
 [[Category:Linux Clients]]
 [[Category:Computers Available on the CS Network]]
 [[Category:Troubleshooting]]

@@ Line 14: / Line 14: @@
 ** ''Ugrad Net'' users have a [[Disk Quotas|disk quota]] to prevent that.
 ** ''Grad/Research Net'' users do not have specific disk quotas but must realize that they  share their disk space with faculty, staff, researchers, other students, etc. So, they must pay close attention to the disk space they use.
-** Disk space not only included your home directory, but can also include your use of the Linux systems's '''/tmp''' directory as well.
+** Disk space not only includes your home directory, but can also include your use of the Linux systems's '''/tmp''' directory as well.
 ==Typical Symptoms of Exceeding Computer Resources on Our Linux Systems==

@@ Line 13: / Line 13: @@
 * Disk space
 ** ''Ugrad Net'' users have a [[Disk Quotas|disk quota]] to prevent that.
-** ''Grad/Research Net'' users do not have specific disk quotas but must realize that they  share their disk space with faculty, staff, etc. So, they must pay close attention to the disk space they use.
+** ''Grad/Research Net'' users do not have specific disk quotas but must realize that they  share their disk space with faculty, staff, researchers, other students, etc. So, they must pay close attention to the disk space they use.
 ** Disk space not only included your home directory, but can also include your use of the Linux systems's '''/tmp''' directory as well.

@@ Line 26: / Line 26: @@
 ==Who Is Affected When Your Program Uses Up Resources on One of Our Linux Systems?==
-:<span style="color:#ff0000">Because all our our CS Linux computers are '''multiuser''' systems, programs that exceed the computer's resources, slowing down the system, could potentially affect '''''all''''' the users logged into those systems, remotely, or at the actual computer console.</span>
+:{{red|Because all our our CS Linux computers are '''multiuser''' systems, programs that exceed the computer's resources, slowing down the system, could potentially affect '''''all''''' the users logged into those systems, remotely, or at the actual computer console.}}
 :Exceeding the computer's resources could also affect programs running in the background, perhaps as part of the computer's own system software or other users' batch jobs.

@@ Line 87: / Line 87: @@
 Every process on our systems has a priority, which defaults to 0, signifying a neutral priority.  Higher numbers, up to 20, represent ''lower'' priorities; the programs are being "nice" and allowing other programs to run more often.  A priority of 10 is twice as nice as a priority of 5, and half as nice as a priority of 20.  (Negative numbers, from -1 down to -20, represent very ''high'' priorities and are reserved for system processes.)
-To change a process' priority, use the '''<code>renice</code>''' command:
+To ''change'' a process' priority, use the '''<code>renice</code>''' command:
   <kbd>renice <var>priority</var> <var>pid</var></kbd>
-"<var>priority</var>" gives the new priority for the process, from 1 to 20.  Note that ''you can only ever raise the priority number''; once a process is at, say, 10, you can raise it to 15 but you cannot lower it to 5.
+:"<var>priority</var>" gives the new priority for the process, from 1 to 20.  Note that ''you can only ever raise the priority number''; once a process is at, say, 10, you can raise it to 15 but you cannot lower it to 5.
-"<var>pid</var>" is the process ID for your process.  You can get that from <code>top</code> or <code>ps</code>, [[#Monitoring Your Processes' Memory and CPU Usage with Linux Commands|as described above]].
+:"<var>pid</var>" is the process ID for your process.  You can get that from <code>top</code> or <code>ps</code>, [[#Monitoring Your Processes' Memory and CPU Usage with Linux Commands|as described above]].
-To set a process' priority when you start it, use the '''<code>nice</code>''' command:
+To set a process' priority ''when you start it'', use the '''<code>nice</code>''' command:
   <kbd>nice <var>your program ...</var></kbd>

@@ Line 34: / Line 34: @@
 ==Tips to Prevent Your Programs from Exceeding the System Resources on Our Computers==
-*  Try to design your programs and/or datasets so that their running memory requirements don't exceed the capabilities of the system they're running on.  Therefore, become familiar with the specs of our CS Linux systems:
+*  Try to design your programs and/or datasets so that their running memory requirements '''do not exceed''' the capabilities of the system they're running on.  Therefore, become familiar with the specs of our CS Linux systems:
 ** [[Linux_Clients_on_the_CS_Grad/Research_Net|Specs on our Grad/Research Net Linux Computers]]
 ** [[Linux_Clients_on_the_CS_Undergrad_Net|Specs on our Ugrad Net Linux Computers]]
-* Try to avoid using the system's complete RAM memory as much as possible.  Put safeguards into your programs to monitor your use of memory.
+* Try to '''avoid using the system's complete RAM memory''' as much as possible.  Put safeguards into your programs to monitor your use of memory.
-* Try to run your programs during low-demand times of day (mornings are best; late evenings are the most busy.)
+* Try to '''run your programs during low-demand times of da'''y (mornings are best; late evenings are the most busy.)
-* Try not to tie up the computer's resources for longer than the program needs to run.
+* Try '''not to tie up the computer's resources for longe'''r than the program needs to run.
 :: '''Do not forget that you are running programs.'''  One of the biggest areas we've had issues with is that some users start their programs in the background and forget that the programs are still running. And in some cases, the programs have issues and start using more resources than actually needed.

← Older revision		Revision as of 21:36, 1 September 2021
Line 104:		Line 104:
	==And, Worth Mentioning Again...==		==And, Worth Mentioning Again...==
	: Please remember that because these are multiuser systems, ''other users could be logged into the system and could be affected if your running program exceeds the computer's resources.''		: Please remember that because these are multiuser systems, ''other users could be logged into the system and could be affected if your running program exceeds the computer's resources.''
		+
		+	[[Category:Linux Clients]]
		+	[[Category:Computers Available on the CS Network]]
		+	[[Category:Troubleshooting]]

@@ Line 1: / Line 1: @@
-==INTRO==
+== Introduction ==
-:As part of being a Computer Science student, you will no doubt create and run your own programs on our [https://support.cs.jhu.edu/wiki/Category:Linux_Clients CS Linux Systems]   You also might be downloading programs from elsewhere and running then on our systems as well.
+:As part of being a Computer Science student, you will no doubt create and run your own programs on our [[:Category:Linux_Clients|CS Linux Systems]].  You also might be downloading programs from elsewhere and running then on our systems as well.
 :It's possible that software you write (or software you've downloaded and run) could, when running, exceed the existing resources on our systems.
-==Computing System Resources That Could Be Exceeded==
+== Computing System Resources that Could Be Exceeded ==
 * Memory (RAM)
@@ Line 12: / Line 12: @@
 * Disk space
-** ''Ugrad Net'' users have a [https://support.cs.jhu.edu/wiki/Disk_Quotas disk quota ]  to prevent that.
+** ''Ugrad Net'' users have a [[Disk Quotas|disk quota]] to prevent that.
 ** ''Grad/Research Net'' users do not have specific disk quotas but must realize that they  share their disk space with faculty, staff, etc. So, they must pay close attention to the disk space they use.
 ** Disk space not only included your home directory, but can also include your use of the Linux systems's '''/tmp''' directory as well.
-==Typical Symptoms Of Exceeding Computer Resources On Our Linux Systems==
+==Typical Symptoms of Exceeding Computer Resources on Our Linux Systems==
 * Timeouts ssh'ing into the computer.
@@ Line 24: / Line 24: @@
 * Programs stop running because they run out of RAM or swap disk space.
-==Who Is Affected When Your Program Uses Up Resources On One Of Our Linux Systems?==
+==Who Is Affected When Your Program Uses Up Resources on One of Our Linux Systems?==
 :<span style="color:#ff0000">Because all our our CS Linux computers are '''multiuser''' systems, programs that exceed the computer's resources, slowing down the system, could potentially affect '''''all''''' the users logged into those systems, remotely, or at the actual computer console.</span>
@@ Line 32: / Line 32: @@
 :'''''So... always be aware that you are not necessarily the only one logged into a system when you're running your own programs.'''''
-==Tips To Prevent Your Programs From Exceeding The System Resources On Our Computers==
+==Tips to Prevent Your Programs from Exceeding the System Resources on Our Computers==
 *  Try to design your programs and/or datasets so that their running memory requirements don't exceed the capabilities of the system they're running on.  Therefore, become familiar with the specs of our CS Linux systems:
-** [https://support.cs.jhu.edu/wiki/Linux_Clients_on_the_CS_Grad/Research_Net Specs on our Grad/Research Net Linux Computers ]
+** [[Linux_Clients_on_the_CS_Grad/Research_Net|Specs on our Grad/Research Net Linux Computers]]
-** [https://support.cs.jhu.edu/wiki/Linux_Clients_on_the_CS_Undergrad_Net Specs on our Ugrad Net Linux Computers]
+** [[Linux_Clients_on_the_CS_Undergrad_Net|Specs on our Ugrad Net Linux Computers]]
 * Try to avoid using the system's complete RAM memory as much as possible.  Put safeguards into your programs to monitor your use of memory.
@@ Line 48: / Line 48: @@
 ::'''Therefore... ''please make sure you check in on your running programs often, and use monitoring tools to make sure you are not exceeding resources.'''''
-==Monitoring Your Processes' Memory and CPU Usage With Linux Commands==
+==Monitoring Your Processes' Memory and CPU Usage with Linux Commands==
 :Use the '''top''' or '''htop''' programs to see your program's stats.
 :* '''top'''
@@ Line 55: / Line 55: @@
 :** htop -u ''username''
 :** htop --user=''username''
-:* '''ps''' (coming soon)
+:* '''ps'''
-==Ending Or Modifying Your Running Process Using Linux Commands==
+==Ending or Modifying Your Running Process Using Linux Commands==
-===Ending A Process===
+===Ending a Process===
-:* '''kill''' - end a process
 :** First, determine process ID (PID)
-:** Generally best to choose the ___ [https://www.tecmint.com/how-to-kill-a-process-in-linux kill signal]
+:** Start by sending the HUP [https://www.tecmint.com/how-to-kill-a-process-in-linux signal]
-:***  Example: Kill process with PID 15476 using kill signal _____:
+:***  Example: Kill process with PID 15476 using signal HUP:
-:**** ''kill -____ 15476''
+:**** <code>kill -HUP 15476</code>
-:* '''pkill''' - end a process
+:** If the process is still running, use the TERM signal.  (This is the default signal if one is not specified.)
-:** First, determine process ID (PID)
+:*** e.g.: <code>kill -TERM ''15476''</code>
-:** Determine appropropriate [https://www.tecmint.com/how-to-kill-a-process-in-linux kill signal]
+:** If the process is ''still'' running, use the KILL signal.  This forces the process to exit, without allowing it to clean up after itself, so it's recommended only of the other two signals don't have an effect.  (Some online references refer to "<code>kill -9</code>"; that the same as "<code>kill -KILL</code>".)
-:***Example: to kill all processes owned by you (with your username being ''csstar'')
+:*** e.g.: <code>kill -KILL ''15476''</code>
-:****'''pkill -9 -u ''csstar'''''  (this example will also kill your logged-in shell process.)
-:* Within '''top''' command
+:* '''pkill''' - send a signal to ''all'' processes that match the given criteria.
 :** Find desired process ID (PID)
-:** press ''k'' (for ''kill'')
+:** press '''k''' (for ''kill'')
 :** enter PID at prompt.
-:** enter [https://www.tecmint.com/how-to-kill-a-process-in-linux kill signal]
+:** enter signal number to use (as with <code>kill</code> above, it often works best to try 1 (HUP) first, then 15 (TERM), followed by 9 (KILL).
-===Modifying A Process's Running Priority===
+If you don't give a priority via the <code>-n</code> parameter, it defaults to a priority of 10.
 ==And, Worth Mentioning Again...==
 : Please remember that because these are multiuser systems,  ''other users could be logged into the system and could be affected if your running program exceeds the computer's resources.''