570965 - need statistical garbage reclamation selftest

Status: RESOLVED WONTFIX

(Tamarin Graveyard :: Garbage Collection (mmGC), defect)

Description

[Felix S. Klock II [:pnkfelix, :fklock]]

Lars has convinced me that trying to make a selftest (of e.g. weak references) that has 100% precision is not reasonable.  Lars suggests a statistical approach instead: rather than check that all known garbage is reclaimed, instead check that some large percentage of it is.

This sounds like a promising tack, at least for the near term.  To my knowledge, none of the existing tests employ such a strategy.  It would be good to have at least one that gets reviewed by the group, to serve as a model template.

Question: what is a reasonable minimal percentage to guarantee gets reclaimed?

I suppose the answer depends on where the float retention is coming from.  My (unconfirmed) hypothesis so far as been that some of the retention is due to the OS adding non-zeroed padding on the stack (to keep certain points at aligned addresses, an issue I've wrestled with in the past for FFI stuff), this would indicate that the expected accidental retention is a function of what we expect the stack frame size to be.  But I should really confirm that hypothesis before making calculations based on it.

Comment 1

[Sylvestre Ledru [:Sylvestre]]

Tamarin isn't maintained anymore. WONTFIX remaining bugs.