[Info-vax] High resolution per-process CPU consumption statistics

[johnwallace4 at yahoo.co.uk]

On Tuesday, 24 March 2020 17:05:24 UTC, Mark Daniel  wrote:
> On 24/3/20 9:24 pm, johnwallace4 at yahoo.co.uk wrote:
> > On Tuesday, 24 March 2020 00:02:22 UTC, Mark Daniel  wrote:
> >> Would like to be able to measure process CPU consumed during specified
> >> continuous sections of processing.  Only interested in CPU-intensive
> >> sections so USER mode consumed relevant.  Imagine inserting calls at the
> >> beginning and ending of those sections with a magic number representing
> >> CPU consumption/delta/whatever made available.
> >>
> >> As some of these CPU-intensive code sections are short duration the
> >> granularity needs to be quite fine.  The likes of JPI$_CPUTIM and
> >> LIB$STAT_TIMER (10mS) seem unsuitable.
> >>
> >> Prepared for non- USER mode code.  This is only for ad hoc developmental
> >> insight and not general use.  Needs to accommodate Alpha and/or Itanium
> >> (and/or x86-64 :-)
> >>
> >> And, of course, any other suggestion.
> >>
> >> As always, TIA.
> > 
> > Is it safe to assume that the code in question is single-threaded?
> 
> Yes.
> 
> > Is it safe to assume that the code in question is running on a
> > single-processor system?
> 
> Yes.
> 
> > Is an Alpha-only solution better than nothing at all?
> 
> Sure.
> 
> > Have a look at RPCC (Read Process Cycle Counter) in the Alpha/VMS
> > PALcode and see if it might help.
> > 
> > See e.g. the Alpha Architecture Reference Manual documentation e.g.
> > http://www.bitsavers.org/pdf/dec/alpha/Sites_AlphaArchitectureReferenceManual_1992.pdf
> > (there's probably more useful RPCC-related stuff available too).
> 
> Before posting here, a fair effort with an unnamed but common search 
> engine and my chosen query strings consistently returned references to 
> that document and section.
> 
> My fevered imagination (but internals hacking very-much limited to 
> monkey-see-monkey-do) has something of the ilk:
> 
>     unsigned __int64  start_count,
>                       end_count;
> 
>     void get_cpu_count (unsigned __int64 *here)
>     {
>        *here = EXE$GL_CURRENT_CPU_COUNT;
>        return SS$_NORMAL;
>     }
> 
>     sys$cmkrnl (&get_cpu_count, &start_count);
>     ...
>     sys$cmkrnl (&get_cpu_count, &end_count);
> 
> Some similar code would be used to obtain the RPCC.
> 
> Thanks for the suggestion John.

I only offered half a suggestion :( (bit pushed for time 
earlier).

Now I'm back and I have clarity on some of your constraints,
I'll try to improve my suggestion. 

Are you writing in C, or do you have access to a C compiler? 
If you have access to Compac C (or similar) for Alpha, 
and/or related documentation, have a look at the __RPCC(void) 
builtin. No programming required (almost).

This from the HP C Users Guide for OpenVMS; other decuments
and/or compilers may be relevant 

///

6.2.1.90 Read Process Cycle Counter ( __RPCC)

The __RPCC function reads the current process cycle counter.

This function has the following format:

uint64 __RPCC (void); 

///


It is left as an exercise for the student to work out how 
this is implemented, e.g. specifically how to use it from 
non-C code (meaning: I used to know, but it's a long time
since I used it and a LOT of memory has become volatile
and error-prone in the intervening years).

You can probably work out how to put another layer on top
to make it a closer fit to your particular needs so you 
can for example generate output along the lines of:

Code block 7 executed 59 times, total 4194303 cycles,
 minimum time: 3 cycles, maximum 47000 cycles.

Or whatever. I'm sure you get the general idea.

Can you say a little more about what you're trying to
achieve here? It may not be appropriate to extrapolate 
results among different members of the Alpha family,
never mind from one processor architecture to a very
different one (Alpha->IA64?). Maybe that doesn't
matter?

Have a lot of fun.