Re: MPS: Loaded pdump

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Helmut Eller <eller.helmut@gmail.com> writes:

> On Thu, May 09 2024, Gerd Möllmann wrote:
>
>> No idea. I've only looked at telemetry to see if it had something
>> helping me debug things. I didn't see anything obvious doing that at the
>> time. Maybe you could just add the PROT and see what the difference is?
>
> There is an RootScan event. I don't know what the best way would be to
> figure out the duration from that.  I simply used the difference to the
> next RootScan event.  This query
>
> select root,label,avg(delta),min(delta),max(delta) from (select root,
> (select I.string from  EVENT_Intern AS I,  EVENT_Label AS L where
> I.stringId = L.stringId and R.root=L.address) as label,time, time -
> lag(time) over(order by time) as delta from EVENT_RootScan R) group by
> root order by avg(delta) desc limit 5;
>
> prints:
>
> root             label        avg(delta)     min(delta)  max(delta)
> ---------------  -----------  -------------  ----------  ----------
> 139759443775512  (null)       1958814868.6   1889481499  2809291196
> 139759443778736  "pdump root  35339296.0625  34952012    36923554  
> 139759443779272  (null)       960551.25      926604      1113924   
> 139759443778864  (null)       328300.75      274522      414676    
> 139759443776656  (null)       306938.6875    199500      411674    
>
> I'm not sure this makes any sense.  The first line could be for a root
> that is always scanned as the last per flip; that's why the delta is
> larger than for the pdump root.
>
> So (/ 35e6 2.5e9) would give again 14 milliseconds.  Can that be?

This is what I understood:

Bahnhof. No :-)

I think EVENT_Label is a table you made that maps addresses of roots to
a label. The delta is the # of ticks, or most likely it is ticks,
between events, averaged. And the ticks divided by you cpu spped = time
taken for a pdump root scan = 14 ms which is ca. what a flip takes.
Right?

I find that at least not completely implausible. Maybe scanning the
pdump root dominates how long a flip takes. Could be.

> The MPS_RM_PROT flag didn't make much difference, beyond the noise
> that's already there.

Ok pity, then we can probably forget about that idea. For the moment.