Re: load average calculation failing

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On May  9 10:45, Corinna Vinschen wrote:
> Mark, did you try to add the computer name to the path by calling
> GetComputerName() in load_init?
> 
> I tried the patch I pasted to the end of this mail, but it did not help
> the first PdhGetFormattedCounterValue call in get_load to return
> success.
> 
> > > 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. :-(
> > > 
> > 
> > Thanks for looking into this.
> > You can find the user space version of this code I initially wrote at
> > https://github.com/jon-turney/windows-loadavg, which might save you some
> > time.
> > 
> > I can't reproduce this on W10 21H1, so I think this must be due to some
> > change in later Windows...
> 
> I can reproduce this on W10 21H1, too, and the problem is the one
> I outlined above, with load_init working fine and just the
> PdhGetFormattedCounterValue failing in get_load.

Btw, the other patch, which makes loadavg work for me, is the
below one.  It just doesn't really make me happy.


diff --git a/winsup/cygwin/loadavg.cc b/winsup/cygwin/loadavg.cc
index 127591a2e1f5..e08c13c86de6 100644
--- a/winsup/cygwin/loadavg.cc
+++ b/winsup/cygwin/loadavg.cc
@@ -40,6 +40,7 @@
 #include <time.h>
 #include <sys/strace.h>
 #include <pdh.h>
+#include <pdhmsg.h>
 
 static PDH_HQUERY query;
 static PDH_HCOUNTER counter1;
@@ -95,18 +96,33 @@ static bool load_init (void)
 /* estimate the current load */
 static bool get_load (double *load)
 {
+  PDH_STATUS ret;
+  PDH_FMT_COUNTERVALUE fmtvalue1;
+  bool tried_again = false;
+
   *load = 0.0;
 
-  PDH_STATUS ret = PdhCollectQueryData (query);
+try_again:
+
+  ret = PdhCollectQueryData (query);
   if (ret != ERROR_SUCCESS)
     return false;
 
   /* Estimate the number of running processes as (NumberOfProcessors) * (%
      Processor Time) */
-  PDH_FMT_COUNTERVALUE fmtvalue1;
   ret = PdhGetFormattedCounterValue (counter1, PDH_FMT_DOUBLE, NULL, &fmtvalue1);
   if (ret != ERROR_SUCCESS)
-    return false;
+    {
+      if (ret == (PDH_STATUS) PDH_INVALID_DATA
+	  && fmtvalue1.CStatus == PDH_CSTATUS_INVALID_DATA
+	  && !tried_again)
+	{
+	  tried_again = true;
+	  Sleep (1000L);
+	  goto try_again;
+	}
+      return false;
+    }
 
   double running = fmtvalue1.doubleValue * wincap.cpu_count () / 100;