Re: [patch 3/3] convert CONFIG tag for extended accounting routines

[Jay Lan]

Jay Lan wrote:
> Andrew Morton wrote:

[snip]

> > > +        if (delta == 0)
> > > +            return;
> > > +        tsk->acct_stimexpd = tsk->stime;
> > > +        tsk->acct_rss_mem1 += delta * get_mm_rss(tsk->mm);
> > > +        tsk->acct_vm_mem1 += delta * tsk->mm->total_vm;
> >
> >
> >
> > It's a bit weird to be multiplying RSS by time.  What unit is a "byte
> > second"?
> >
> > If this is not a bug then I guess this is an intermediate term for
> > additional downstream processing.  There is information loss here and I'd
> > have thought that it would be better to simply send `delta' and the rss
> > straight to userspace, let userspace work out what math it wants to 
> > perform
> > on it.  If that makes sense?
> >
> > I see that the code has been like this for a long time, so treat this 
> > as a
> > "please educate me about BSD accounting" email ;)
>
>
> This is not a BSD accounting thing. It came from UNICOS and IRIX.
> I am pinging the person who knows how the real world users use these
> two fields...

Andrew,

Here is the explanation i owe you.

We accumulated the RSS/VM value at each timer interrupt update in terms
of pages-tick. At userland, the value is divided by tsk->stime (in usec)
to gain average usage of RSS/VM.

I need to do a little bit more processing in the kernel to convert
the pages-tick values to Mbytes-usec unit before delivery to userland
since the calculation are platform dependent. I will include the
change in the upcoming update patch.

Regards,
 - jay


> Regards,
>  - jay
>
> >

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