load average calculation failing

[Mark Geisert]

Mark Geisert wrote (on the main Cygwin mailing list):
> I've recently noticed that the 'xload' I routinely run shows zero load even with 
> compute-bound processes running.  This is on both Cygwin pre-3.4.0 as well as 
> 3.3.4.  A test program, shown below, indicates that getloadavg() is returning with 
> 0 status, i.e. not an error but no elems
> of the passed-in array updated.
> 
> Stepping with gdb through the test program seems weird within the 
> loadavginfo::load_init method.  Single-stepping at line loadavg.cc:68 goes to 
> strace.h:52 and then to _sigbe ?!
> 
> I had recently updated both Cygwin and Windows 10 to latest at the same time so I 
> cannot say when the failure started.  Last day or two at most.
> 
> ..mark
> 
> -------------------
> #define _GNU_SOURCE
> #include <stdio.h>
> #include <stdlib.h>
> 
> int
> main (int argc, char **argv)
> {
>      double loadavg[3];
> 
>      int res = getloadavg (loadavg, 3);
>      if (res == -1)
>          return 0xFF;
>      if (res > 0)
>          for (int i = 0; i < res; i++)
>              printf ("%f.2 ", loadavg[i]);
> 
>      return res;
> }

I've debugged a bit further..  Within Cygwin's loadavg.cc:load_init(), the 
PdhOpenQueryW() call returns successfully.  The subsequent PdhAddEnglishCounterW() 
call is unsuccessful.  It returns status 0x800007D0 == PDH_CSTATUS_NO_MACHINE. 
The code (at line 68 mentioned above) calls debug_printf() to conditionally 
display the error, which is what leads to the strace.h and _sigbe; that's fine.

The weird PDH_CSTATUS_NO_MACHINE is the problem.  I'll try running the example 
from an elevated shell.  Or rebooting the machine.  After that it's consulting 
some oracle TBD. :-(

..mark