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127 lines
6.0 KiB
Plaintext
127 lines
6.0 KiB
Plaintext
The following is a demonstration of the iopending tool,
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Here we run it with a sample interval of 1 second,
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# iopending 1
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Tracing... Please wait.
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2006 Jan 6 20:21:59, load: 0.02, disk_r: 0 KB, disk_w: 0 KB
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value ------------- Distribution ------------- count
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< 0 | 0
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0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1010
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1 | 0
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2006 Jan 6 20:22:00, load: 0.03, disk_r: 0 KB, disk_w: 0 KB
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value ------------- Distribution ------------- count
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< 0 | 0
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0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1000
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1 | 0
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2006 Jan 6 20:22:01, load: 0.03, disk_r: 0 KB, disk_w: 0 KB
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value ------------- Distribution ------------- count
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< 0 | 0
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0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1000
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1 | 0
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^C
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The iopending tool samples at 1000 Hz, and prints a distribution of how many
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disk events were "pending" completion. In the above example the disks are
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quiet - for all the samples there are zero disk events pending.
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Now iopending is run with no arguments. It will default to an interval of 5
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seconds,
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# iopending
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Tracing... Please wait.
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2006 Jan 6 19:15:41, load: 0.03, disk_r: 3599 KB, disk_w: 0 KB
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value ------------- Distribution ------------- count
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< 0 | 0
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0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 4450
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1 |@@@ 390
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2 |@ 80
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3 | 40
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4 | 20
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5 | 30
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6 | 0
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^C
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In the above output there was a little disk activity. For 390 samples there
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was 1 I/O event pending; for 80 samples there was 2, and so on.
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In the following example iopending is run during heavy disk activity. We
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print output every 10 seconds,
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# iopending 10
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Tracing... Please wait.
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2006 Jan 6 20:58:07, load: 0.03, disk_r: 25172 KB, disk_w: 33321 KB
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value ------------- Distribution ------------- count
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< 0 | 0
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0 |@@@@@@@@@ 2160
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1 |@@@@@@@@@@@@@@@@@@@@@@@@@@@ 6720
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2 |@@@@ 1000
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3 | 50
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4 | 30
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5 | 20
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6 | 10
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7 | 10
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8 | 10
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9 | 0
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2006 Jan 6 20:58:17, load: 0.05, disk_r: 8409 KB, disk_w: 12449 KB
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value ------------- Distribution ------------- count
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< 0 | 0
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0 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 7260
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1 |@@@@@@@ 1700
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2 |@ 300
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3 | 0
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4 | 10
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5 | 10
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6 | 10
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7 | 20
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8 | 0
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9 | 0
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10 | 0
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11 | 0
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12 | 0
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13 | 0
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14 | 0
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15 | 0
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16 | 0
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17 | 10
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18 | 20
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19 | 0
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20 | 0
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21 | 0
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22 | 0
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23 | 0
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24 | 0
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25 | 0
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26 | 0
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27 | 0
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28 | 0
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29 | 0
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30 | 0
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31 | 10
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>= 32 |@@@ 650
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^C
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In the first output, most of the time (67%) there was 1 event pending,
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and for a short time there were 8 events pending. In the second output we
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see many samples were off the scale - 650 samples at 32 or more pending
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events. For this sample I had typed "sync" in another window, which
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queued many disk events immediately which were eventually completed.
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