Example of mmpmon rhist nr request

This topic is an example of using rhist nr to change the request histogram facility request size and latency changes.

Assume that commandFile contains this line:

rhist nr 512;1m;4m 1.3;4.5;10

and this command is issued:

mmpmon -p -i commandFile

The output is similar to this:

_rhist_ _n_ 199.18.2.5 _nn_ node1 _req_ nr 512;1m;4m 1.3;4.5;10 _rc_ 0 _t_ 1078929833 _tu_ 765083

If the -p flag is not specified, the output is similar to:

mmpmon node 199.18.1.8 name node1 rhist nr 512;1m;4m 1.3;4.5;10 OK

In this case, mmpmon has been instructed to keep a total of 32 counters. There are 16 for read and 16 for write. For the reads, there are four size ranges, each of which has four latency ranges. The same is true for the writes. They are as follows:


size range            0   to   512    bytes
  latency range       0.0   to   1.3    milliseconds
  latency range       1.4   to   4.5    milliseconds
  latency range       4.6   to  10.0    milliseconds
  latency range       10.1 and greater  milliseconds
size range          513   to  1048576 bytes
  latency range       0.0   to   1.3    milliseconds
  latency range       1.4   to   4.5    milliseconds
  latency range       4.6   to  10.0    milliseconds
  latency range       10.1 and greater  milliseconds
size range       1048577  to  4194304 bytes
  latency range       0.0   to   1.3    milliseconds
  latency range       1.4   to   4.5    milliseconds
  latency range       4.6   to  10.0    milliseconds
  latency range       10.1 and greater  milliseconds
size range       4194305 and greater bytes
  latency range       0.0   to   1.3    milliseconds
  latency range       1.4   to   4.5    milliseconds
  latency range       4.6   to  10.0    milliseconds
  latency range       10.1 and greater  milliseconds

In this example, a read of size 15 MB that completes in 17.8 milliseconds would fall in the last latency range listed here. When this read completes, the counter for the last latency range is increased by one.

An _rc_ value of 16 indicates that the histogram operations lock is busy. Retry the request.

An example of an unsuccessful response is:

_rhist_ _n_ 199.18.2.5 _nn_ node1 _req_ nr 512;1m;4m 1;4;8;2 _rc_ 22 _t_ 1078929596 _tu_ 161683

If the -p flag is not specified, the output is similar to:

mmpmon node 199.18.1.8 name node1 rhist nr 512;1m;4m 1;4;8;2 status 22 range error

In this case, the last value in the latency range, 2, is out of numerical order.

Note that the request rhist nr = = does not make any changes. It is ignored.

For information on interpreting mmpmon output results, see Other information about mmpmon output.