[Vm-dev] [Pharo-dev] [NB] Trying to implement a ReadStream on NBExternalAddress

Eliot Miranda eliot.miranda at gmail.com
Wed Sep 25 18:36:37 UTC 2013

On Wed, Sep 25, 2013 at 10:39 AM, tim Rowledge <tim at rowledge.org> wrote:

> On 25-09-2013, at 9:30 AM, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> >  Off the top of my head it may need the memory manager to add a "sliver"
> object type, an 8-byte header with no fields, that is collected by
> coallescing with adjacent free blocks, that can fill in the 8-byte gaps
> aligning pinned objects on 16 byte boundaries would create.  I'll think
> about this.
> >
> Wild-ass suggestion; would it work to allocate the relevant object (which
> I'm assuming here is essentially an UninterpretedBytes) with an 'extra' 8
> bytes and then store the 'real' bits at the right place to have the 16byte
> boundary? Yes, there would have to be magic to signify where the  real
> start of data is. Yes, it would potentially change on scavenge, but since
> these are largely pinned, not such a big issue maybe?

In general that's a bad idea because it loads the frequent path (accessing
the object) with the work, unloading the infrequent path (pinning the
object).  It can't happen during scavenge because by definition pinned
objects are not in new space.  hence I think the time to take the hit is on
pinning (an infrequent operation).  Make sense?

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