Backport of estat updates for 6.0.7.0

[brad-lewis]

This includes three issues:

Update estat iscsi, zvol, and zpl scripts. (#55)
LPX-72556 estat warning messages (#52)

It was not a clean merge as the zvol.c script had extra definitions related to this pr. That was no longer needed for aws. Additionally the version of zfs on stage sill uses uio_t so there is not need to change to zfs_uio_t.

I ran all the estat scripts and all compiled and executed though some had no events to record(as expected):

sudo ./estat.py backend-io 1
WARNING: kprobe: blk_start_request - not found
02/03/21 - 22:52:17 UTC

 Tracing enabled... Hit Ctrl-C to end.
   microseconds                                                   write 
value range                 count ------------- Distribution ------------- 
[700, 800)                      1 |@                                       
[800, 900)                      2 |@@@@@@@                                 
[900, 1000)                     2 |@@@@@@@                                 
[1000, 2000)                    1 |@                                       

                                       iops(/s)  avg latency(us)       stddev(us)  throughput(k/s)
write                                         5              936            24632               60


                                       iops(/s)  throughput(k/s)
total                                         6               72


sudo ./estat.py iscsi 1
02/03/21 - 22:52:21 UTC

 Tracing enabled... Hit Ctrl-C to end.
sudo ./estat.py metaslab-alloc 1
02/03/21 - 22:52:26 UTC

 Tracing enabled... Hit Ctrl-C to end.
   microseconds                                      /dev/xvdb1, success
value range                 count ------------- Distribution ------------- 
[10, 20)                        2 |@@@@@@@@@@@@@@@@@@@@@                   

   microseconds                                      /dev/xvdc1, success
value range                 count ------------- Distribution ------------- 
[10, 20)                        2 |@@@@@@@@@@@@@@@@@@@@@                   

   microseconds                                      /dev/xvdd1, success
value range                 count ------------- Distribution ------------- 
[10, 20)                        1 |@                                       

                                       iops(/s)  avg latency(us)       stddev(us)  throughput(k/s)
/dev/xvdb1, success                           2               13               15               72
/dev/xvdc1, success                           2               14               14               72
/dev/xvdd1, success                           1               17                0               36


                                       iops(/s)  throughput(k/s)
total                                         5              180


sudo ./estat.py nfs 1
02/03/21 - 22:52:32 UTC

 Tracing enabled... Hit Ctrl-C to end.
sudo ./estat.py nfs-by-client 1
02/03/21 - 22:52:38 UTC

 Tracing enabled... Hit Ctrl-C to end.
sudo ./estat.py zio 1
02/03/21 - 22:52:42 UTC

 Tracing enabled... Hit Ctrl-C to end.
   microseconds                                             write, syncw
value range                 count ------------- Distribution ------------- 
[700, 800)                      2 |@@@@@@                                  
[800, 900)                      4 |@@@@@@@@@@@@@@@@@@                      
[200000, 300000)                1 |@                                       

                                       iops(/s)  avg latency(us)       stddev(us)  throughput(k/s)
write, syncw                                  7            37943       -937765531               84


                                       iops(/s)  throughput(k/s)
total                                         7               84


sudo ./estat.py zio-queue 1
02/03/21 - 22:52:46 UTC

 Tracing enabled... Hit Ctrl-C to end.
   microseconds                                             write, syncw
value range                 count ------------- Distribution ------------- 
[0, 10)                         5 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@       

                                       iops(/s)  avg latency(us)       stddev(us)  throughput(k/s)
write, syncw                                  5                4                4               68


                                       iops(/s)  throughput(k/s)
total                                         5               68


sudo ./estat.py zpl 1
02/03/21 - 22:52:50 UTC

 Tracing enabled... Hit Ctrl-C to end.
sudo ./estat.py zil -c 1
 Tracing enabled... Hit Ctrl-C to end.
^C02/03/21 - 22:53:21 UTC

   latency                                               zfs_write async
value range                 count ------------- Distribution ------------- 
[4, 8)                         13 |@@@                                     
[8, 16)                         5 |@                                       
[16, 32)                       36 |@@@@@@@@                                
[32, 64)                      112 |@@@@@@@@@@@@@@@@@@@@@@@@                
[64, 128)                      17 |@@@@                                    
[128, 256)                      5 |@                                       

                                            avg
zfs_write async                              45


sudo ./estat.py txg
        date                 txg     time since last sync
         |                    |         |   sync time
         |                    |         |        |  (%% pass 1)
         |                    |         |        |    |     highest dirty (%%) 
         |                    |         |        |    |           |  highest throttle delay
         |                    |         |        |    |           |            |      |  avg delay
         v                    v         v        v    v           v            v      v       v
Wed Feb  3 22:53:30 2021       2989     0ms    17ms (91 pass 1)   2MB ( 0)    0us     0ms    0ms
Wed Feb  3 22:53:35 2021       2990  5102ms    14ms (91 pass 1)   3MB ( 0)    0us     0ms    0ms
^Csudo ./estat.py arc_prefetch
02/03/21 - 22:53:45 UTC

prefetch hit count   : 22
   microseconds                                         arc read latency
value range                 count ------------- Distribution ------------- 
[4, 8)                          1 |@                                       
[16, 32)                        1 |@                                       

                                avg latency(us)
arc read latency                             15


^C02/03/21 - 22:53:46 UTC