sp_sysmon reports high IO in threading mode

[Former Member]

Am looking at sp_sysmon output on an 15.7 SP134 server in thread mode and am seeing very high IO reported even though very little running.

We have 15 threads for default and with just 2 SQL processes running sysmon reports

  Engine Utilization (Tick %)   User Busy   System Busy    I/O Busy        Idle

  -------------------------  ------------  ------------  ----------  ----------

  ThreadPool : syb_default_pool

   Engine 0                         1.5 %         0.0 %      96.1 %       2.5 %

   Engine 1                         3.4 %         0.5 %      93.6 %       2.5 %

   Engine 2                         4.9 %         0.0 %      92.1 %       3.0 %

   Engine 3                         7.4 %         0.0 %      90.6 %       2.0 %

   Engine 4                         5.4 %         0.0 %      92.1 %       2.5 %

   Engine 5                         1.5 %         0.0 %      96.1 %       2.5 %

   Engine 6                         7.4 %         0.0 %      90.1 %       2.5 %

   Engine 7                         4.4 %         0.0 %      92.6 %       3.0 %

   Engine 8                         9.4 %         0.0 %      88.2 %       2.5 %

   Engine 9                        13.3 %         1.0 %      83.3 %       2.5 %

   Engine 10                       11.8 %         0.0 %      85.2 %       3.0 %

   Engine 11                        6.4 %         0.0 %      91.6 %       2.0 %

   Engine 12                       12.8 %         0.0 %      85.2 %       2.0 %

   Engine 13                       11.8 %         0.0 %      86.2 %       2.0 %

   Engine 14                        3.9 %         0.0 %      93.6 %       2.5 %

It seems all the engines are I/O busy- but none of the SQL is doing much SAN or network IO.

The average runnable tasks show little activity

  Average Runnable Tasks            1 min         5 min      15 min  % of total

  -------------------------  ------------  ------------  ----------  ----------

  ThreadPool : syb_default_pool

   Global Queue                       0.0           0.0         0.1       0.0 %

   Engine 0                           0.2           0.7         0.8       8.3 %

   Engine 1                           0.4           1.0         1.0      19.3 %

   Engine 2                           0.1           0.9         0.9       5.2 %

   Engine 3                           0.1           0.7         0.8       5.3 %

   Engine 4                           0.1           0.6         0.7       5.7 %

   Engine 5                           0.1           0.7         0.8       5.1 %

   Engine 6                           0.2           0.5         0.6       7.2 %

   Engine 7                           0.1           0.5         0.7       5.0 %

   Engine 8                           0.1           0.7         0.8       4.2 %

   Engine 9                           0.2           0.7         0.7       8.9 %

   Engine 10                          0.1           0.5         0.7       6.2 %

   Engine 11                          0.1           0.8         0.8       3.3 %

   Engine 12                          0.1           0.6         0.7       4.2 %

   Engine 13                          0.1           0.7         0.7       2.6 %

   Engine 14                          0.2           0.9         0.9       9.5 %

and the Thread utilisation shows this.

I can't see anything else running and the HK tasks should be pretty much idle.

  Thread Utilization (OS %)     User Busy   System Busy        Idle

  -------------------------  ------------  ------------  ----------

  ThreadPool : syb_blocking_pool : no activity during sample

  ThreadPool : syb_default_pool

   Thread 6    (Engine 0)           2.8 %         0.1 %      97.1 %

   Thread 7    (Engine 1)           6.8 %         0.5 %      92.7 %

   Thread 8    (Engine 2)           6.9 %         0.3 %      92.8 %

   Thread 9    (Engine 3)           8.0 %         0.1 %      91.9 %

   Thread 10   (Engine 4)           8.7 %         0.4 %      90.9 %

   Thread 11   (Engine 5)           3.8 %         0.1 %      96.1 %

   Thread 12   (Engine 6)          15.7 %         0.9 %      83.4 %

   Thread 13   (Engine 7)           8.2 %         0.4 %      91.4 %

   Thread 14   (Engine 😎          17.0 %         0.9 %      82.1 %

   Thread 15   (Engine 9)          17.6 %         0.4 %      82.0 %

   Thread 16   (Engine 10)         19.8 %         1.0 %      79.2 %

   Thread 17   (Engine 11)         13.3 %         0.8 %      85.9 %

   Thread 18   (Engine 12)         24.8 %         1.4 %      73.8 %

   Thread 19   (Engine 13)         18.5 %         0.7 %      80.8 %

   Thread 20   (Engine 14)          7.2 %         0.3 %      92.5 %

  ThreadPool : syb_system_pool

   Thread 21   (NetController)      0.1 %         0.2 %      99.7 %

   Thread 22   (DiskController)     3.2 %         1.2 %      95.6 %

The Disk and the Net Controller show its mostly idle. How does this ties in with the previous info showing IO Busy ?

Any idea if sysmon is correctly reporting IO ? Or if its correct how do I see what could be consuming the IO ?

[Former Member · Accepted solution]

Hi Mike,

When  SAP ASE is running Kernel mode threaded, I/O Busy in sp_sysmon is over weighted.

Currently, when in threaded mode, engines are counted as "I/O Busy" if Adaptive Server has any I/O outstanding and the engine is idle. If there is one I/O outstanding and three engines sitting idle, each engine is counted as "I/O Busy".

That sp_sysmon report like this we will try to address with change request # 757246 not so easy as thread mode change the way engine works.

see also the manual

Adaptive Server Enterprise 15.7 ESD #2 > Performance and Tuning Series: Monitoring Adaptive Server w...

Niclas

[Former Member · Accepted solution]

Ah - thanks for the reply.

I'll ignore that section of sysmon.