[dtrace-discuss] Aggregation results do not make any sense

[Alexander Kolbasov]

> Hi Sasha,
> 
> I think the problem you're seeing is that the avg(), min(), and max()
> aggregating actions treat their argument as unsigned while the quantize()
> aggregating action treats it as signed (though max() is obviously printing
> its result as signed).

The values I am dealing with are signed. Is there any reason that avg() min() 
and max() treat their arguments as unsigned? Would it be a useful RFE to have 
signed version of these?
 
> You're obviously dealing with large values -- can you try scaling them
> down before quantizing?

I can, but it seems that here the problem is not with large values but with 
negative values.

- Alex Kolbasov
__
http://blogs.sun.com/akolb

> 
> Adam
> 
> On Tue, Nov 28, 2006 at 01:17:13PM -0800, Alexander Kolbasov wrote:
> > I am using the following simple script on build 51 based bits (it has some
> > kernel changes for CPU caps project) on amd64 with 64-bit kernel.
> > 
> > ----------------------------------------------------------------------
> > #!/usr/sbin/dtrace -s
> > 
> > fbt::ts_exit:entry
> > /execname == "fork"/
> > {
> > 	self->trace++;
> > 	@exits["exits"] = count();
> > }
> > 
> > /*
> >  * cap_project_charge is cpu-caps specific function 
> >  * void cap_project_charge(kproject_t *kpj, int64_t nsecs)
> >  */
> > 
> > fbt::cap_project_charge:entry
> > /self->trace/
> > {
> > 	@f["charge count"] = count();
> > 	@b["charge average"] = avg(arg1);
> > 	@c["charge min"] = min(arg1);
> > 	@d["charge max"] = max(arg1);
> > 	@e["charge quantaized"] = quantize(arg1);
> > }
> > 
> > fbt::ts_exit:return
> > /self->trace/
> > {
> > 	self->trace--;
> > }
> > ----------------------------------------------------------------------
> > 
> > After running for a while, it produces the following strange output. Notice the
> > huge average value and also negative max value and both max and min inconsistent
> > with quantized data:
> > 
> > ----------------------------------------------------------------------
> > dtrace: script './aggbug.d' matched 3 probes
> > ^C
> >   exits                                                         77252
> >   charge count                                                  74274
> >   charge average                                      248360719409675
> >   charge min                                                    28415
> >   charge max                                                 -8697972
> >   charge quantaized                                 
> >            value  ------------- Distribution ------------- count    
> >        -33554432 |                                         0        
> >        -16777216 |                                         98       
> >         -8388608 |@@@                                      5052     
> >         -4194304 |                                         0        
> >         -2097152 |                                         0        
> >         -1048576 |                                         0        
> >          -524288 |                                         0        
> >          -262144 |                                         0        
> >          -131072 |                                         0        
> >           -65536 |                                         0        
> >           -32768 |                                         0        
> >           -16384 |                                         0        
> >            -8192 |                                         0        
> >            -4096 |                                         0        
> >            -2048 |                                         0        
> >            -1024 |                                         0        
> >             -512 |                                         0        
> >             -256 |                                         0        
> >             -128 |                                         0        
> >              -64 |                                         0        
> >              -32 |                                         0        
> >              -16 |                                         0        
> >               -8 |                                         0        
> >               -4 |                                         0        
> >               -2 |                                         0        
> >               -1 |                                         0        
> >                0 |                                         0        
> >                1 |                                         0        
> >                2 |                                         0        
> >                4 |                                         0        
> >                8 |                                         0        
> >               16 |                                         0        
> >               32 |                                         0        
> >               64 |                                         0        
> >              128 |                                         0        
> >              256 |                                         0        
> >              512 |                                         0        
> >             1024 |                                         0        
> >             2048 |                                         0        
> >             4096 |                                         0        
> >             8192 |                                         0        
> >            16384 |                                         1        
> >            32768 |                                         1        
> >            65536 |                                         0        
> >           131072 |                                         8        
> >           262144 |@                                        2336     
> >           524288 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@     66465    
> >          1048576 |                                         313      
> >          2097152 |                                         0        
> > 
> > ----------------------------------------------------------------------
> > 
> > Any clues what is going on?
> > 
> > __
> > - Alexander Kolbasov
> > _______________________________________________
> > dtrace-discuss mailing list
> > dtrace-discuss at opensolaris.org
> 
> -- 
> Adam Leventhal, Solaris Kernel Development       http://blogs.sun.com/ahl
>