Re: Enhancing Memory Context Statistics Reporting

>
>
>
> That's not an argument against moving it to BaseInit() though, as that's
> called before procsignal is even initialized and before signals are
> unmasked.
>

Yes, OK.

> I don't really understand why DSA_DEFAULT_INIT_SEGMENT_SIZE is
> >
> > something that makes sense to use here?
> > >
> > >
> > To determine the memory limit per backend in multiples of
> > DSA_DEFAULT_INIT_SEGMENT_SIZE.
> > Currently it is set to 1 * DSA_DEFAULT_INIT_SEGMENT_SIZE.
> > Since a call to dsa_create would create a DSA segment of this size, I
> > thought it makes sense
> > to define a limit related to the segment size.
>
> I strongly disagree. The limit should be in an understandable unit, not on
> another subystems's defaults that might change at some point.
>

OK, makes sense.

>
>
> > > + /* If the dsm mapping could not be found, attach to the area */
> > > > + if (dsm_seg != NULL)
> > > > + return;
> > >
> > > I don't understand what we do here with the dsm? Why do we not need
> > > cleanup
> > > if we are already attached to the dsm segment?
> > >
> >
> > I am not expecting to hit this case, since we are always detaching from
> the
> > dsa.
>
> Pretty sure it's reachable, consider a failure of dsa_allocate(). That'll
> throw an error, while attached to the segment.
>
>
You are right, I did not think of this scenario.

>
> > This could be an assert but since it is a cleanup code, I thought
> returning
> > would be a harmless step.
>
> The problem is that the code seems wrong - if we are already attached we'll
> leak the memory!
>
>
I understand your concern. One issue I recall is that we do not have a
dsa_find_mapping
function similar to dsm_find_mapping(). If I understand correctly, the only
way to access
an already attached DSA is to ensure we store the DSA area mapping in a
global variable.
I'm considering using a global variable and accessing it from the cleanup
function in case
it is already mapped.
Does that sound fine?

> As I also mentioned, I don't understand why we're constantly
> attaching/detaching from the dsa/dsm either. It just seems to make things
> more
> complicated an dmore expensive.
>

OK, I see that this could be expensive if a process is periodically being
queried for
statistics. However, in scenarios where a process is queried only once for
memory,
statistics, keeping the area mapped would consume memory resources, correct?

Thank you,
Rahila Syed