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Old 01-02-2018, 05:08 AM   #1
barani_pdy
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iostat output interpretation (%util is 100)


Hi,

In my device I am observing the iostat's %util is 100 for /dev/sda5(which is a swap partition).

iostat output:
==============
avg-cpu: %user %nice %system %iowait %steal %idle
0.43 0.00 3.24 0.13 0.00 97.31

Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util
sda 6.41 58.53 0.91 4.53 0.03 0.25 103.52 0.03 4.71 2.24 1.22
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sda3 0.00 1.21 0.01 1.02 0.00 0.01 17.48 0.00 2.46 1.92 0.20
sda4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 100.00
sda5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102481911520607.62 0.00 0.00 100.00
sda6 0.00 22.79 0.01 1.89 0.00 0.10 103.98 0.01 3.32 1.77 0.34
sda7 6.41 34.53 0.89 1.62 0.03 0.14 138.12 0.02 6.68 2.78 0.70
sdb 6.39 58.55 0.87 4.52 0.03 0.25 104.40 0.03 4.97 2.32 1.25
sdb1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdb2 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdb3 0.00 1.21 0.01 1.02 0.00 0.01 17.48 0.00 2.50 1.98 0.20
sdb4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 102481911520607.62 0.00 0.00 100.00
sdb5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 100.00
sdb6 0.00 22.79 0.00 1.89 0.00 0.10 104.26 0.01 3.19 1.66 0.32
sdb7 6.39 34.54 0.87 1.61 0.03 0.14 140.46 0.02 7.36 3.02 0.75


also memory details follows
MemTotal=16325868 MemFree=9407272 Buffers=3264928 Cached=595172 SwapTotal=8388472 SwapFree=8388472

help me in interpreting the cause ?

Rgds,
 
Old 01-02-2018, 06:06 AM   #2
rtmistler
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Try the commands recommended here: https://www.tecmint.com/commands-to-...sage-in-linux/

I think the output of iostat is interpreting that the swap space is "special" and showing that partition at 100%.

Note also that the output you've shown also says the following, at the bottom:
Quote:
MemTotal=16325868 MemFree=9407272 Buffers=3264928 Cached=595172 SwapTotal=8388472 SwapFree=8388472
Therefore your swap space is actually 0% used.

iostat is probably looking at partition usage and swap space is special therefore the partition information is indicating that it is 100% in use.

Last edited by rtmistler; 01-02-2018 at 06:07 AM.
 
Old 01-02-2018, 06:48 AM   #3
sundialsvcs
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Remember that you don't care about "percent utilization" of an I/O channel: "100% is wonderful."

What you care about is queue size, and the amount of time processes are "parked" waiting their turn there.
 
Old 01-03-2018, 07:51 AM   #4
barani_pdy
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Hi rtmistler , sundialsvcs ,

Thanks for your reply.

There are instances where swap partition iostat's %util is not 100.

Also in the earlier post we can observe that when swap is 100% the avgqu-sz is 102481911520607.62

Rgds,

Last edited by barani_pdy; 01-03-2018 at 07:53 AM.
 
  


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