Persistence VM?
Ian Piumarta
ian.piumarta at inria.fr
Mon Aug 19 20:26:10 UTC 2002
On Mon, 19 Aug 2002, Stephen Pair wrote:
> Sounds correct to me, but you meant "with one extra word for each
> compact header" instead of "with one extra word for each non-compact
> header" correct?
I meant "for each header that would become non-compact after giving up on
compact headers".
> Also, even if the cci not zero, isn't it possible for that object to be
> larger than 255 bytes (thus requiring a three word header even though
> it's a compact class)?
Absolutely.
> If so, then even 7% is a tad (but just a tad) high.
FWIW:
ok: 415298 objects in image
type 0 = 5552 ( 1.34%) size+class header
type 1 = 84016 (20.23%) class header
type 3 = 325730 (78.43%) short header
4736 (1.43%) of compact objects have size header
(type 2 doesn't show up because it's the header on the free chunk) so the
real saving from compact headers is
.7843 * 415298 * 4 / 1024 = 1272 kilobytes
rather than the 1290 I quoted earlier.
Ian
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