Visit Our UNIX and Linux User Community


Vmstat


 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers Vmstat
# 1  
Old 09-18-2001
Vmstat

I have MATLAB INSTALLED IN MY SUN MACHINE >>
WHENEVER I USE IT THE CPU USAGE SHOWS ABT 90%
Seeing the vmstat shows that system calls and context switch counters reach a very high value .
What are these counters ( Man pages do not give much info on that) ....
The only thing i can make out that there is a system bottleneck .
Wat steps should i take in such a situation ....

Thanx

DP
# 2  
Old 09-19-2001
System call are those things documented in section 2 of the manual. They are things like open(), read(), fork(), exec(). Each time any program calls any of those, a counter is incremented. vmstat is showing the increments to that counter.

Once a process starts to run, it gets to run until its timeslice runs out. But if it does something like read(), it must wait until the read finishes before it can run some more. When one process stops running for any reason, the kernel must look at the run queues to find another process to run. This operation of allowing another process to run is called a context switch. Again each time it happens, a counter is incremented and vmstat is showing the increments.

If no process is on the run queues, the kernel will repeatedly scan the run queues until a process appears there. While the kernel is scanning the run queues, the system is idle.

A high number of context switches is not good. If the kernel is context switching too often, that 10% idle could be misleading. It might actually be scanning the run queues once 10% of the time rather than looping as it waits for a runnable process.
 

Previous Thread | Next Thread
Test Your Knowledge in Computers #235
Difficulty: Easy
The ARPANET was operated by the military during the two decades of its existence, until 1990.
True or False?

10 More Discussions You Might Find Interesting

1. Linux

Vmstat

I m checking idle time using vmstat, below are the results var=$(ssh wmtmgr@$hostname vmstat | tail -1 | awk '{print $15}') 89 and now im subtracting 89 with 100 & im getting expected results expr 100 - $var 11 Now How can I get the result 11 in one line code? (4 Replies)
Discussion started by: sam@sam
4 Replies

2. Solaris

Vmstat | nawk

I'm trying to parse vmstat output with this: vmstat | nawk '/0/{printf "%s\ \n", $5}' but output is different on two sparc Solaris 10 servers, one is missing line with 'free'. why ? (3 Replies)
Discussion started by: orange47
3 Replies

3. AIX

Need guidance on VMStat

I need some guidance on the differences in observations, not sure how significantly different are they. Also, It would be nice to hear on the values and what the obvious tuning for performance missing. Observation 1 ending vmstat -v 3948544 memory pages ending vmstat -v ... (1 Reply)
Discussion started by: Snipper
1 Replies

4. Shell Programming and Scripting

vmstat

Hi I need to write a script to display VMSTAT every 5 seconds and I just need the memory columns - swap free re and just the numbers and the headers arent required. For example bash-3.00$ vmstat 5| awk '{print $4" "$5" "$6}' disk faults cpu ------ This header isnt required swap... (3 Replies)
Discussion started by: kapilk
3 Replies

5. Linux

vmstat help

Hi everyone, I need to see some VM manager performance/behavior information on some Linux boxes regarding pages scanned/activation of the paging algorithm in order to get an idea if a given server needs more memory and is actually paging. In Aix servers, by using the vmstat cmd you... (1 Reply)
Discussion started by: jcpetela
1 Replies

6. Solaris

Huge PI in vmstat

This is something nowbody around me can explain: vmstat (-S 5) shows a huge number of PI but when I try to monitor it in parallel with iostat - there is no IO activity to be seen that would correspond to this. I have 16G RAM and 32G swap file. I'll really appreciate if somebody can explain it.... (9 Replies)
Discussion started by: dkvent
9 Replies

7. UNIX for Dummies Questions & Answers

vmstat

Hi I wanted to collect data by using vmstat -I 60 >xxxx.txt & using my own account It was stopped by it self after 2 hours try again same result We want to collect day date by succession how to collect data using vmstat for day Thank you (2 Replies)
Discussion started by: Syed_45
2 Replies

8. UNIX for Advanced & Expert Users

vmstat

Hi, what does mean the free colomne in out put of vmstat ? is it free espace of physical memory or of swap space on hard disk ? Thank you (4 Replies)
Discussion started by: big123456
4 Replies

9. UNIX for Dummies Questions & Answers

vmstat

When I exeute vmstat (e.g. vmstat 30 2), in some machines I get some wierd result as the first line. like: -117% or 208% for CPU idle percentage. But the second line is alright. Could someone explain this please. Thanks ! Chaadana (4 Replies)
Discussion started by: chaandana
4 Replies

10. UNIX for Dummies Questions & Answers

vmstat

Hi, In the unix command, "vmstat" we get information on Page memory. what does the "mf" - "minor fault" is? Regards, Anent (3 Replies)
Discussion started by: anent
3 Replies

Featured Tech Videos