I have an idea but it doesn't explain everything; SRTs are used to collect CAFs, and CAFs are always added to the oldest generation's mut_list when allocated [1].
When we're scavenging a mut_list we know we're not doing a major GC, and because mut_list of oldest generation has all the newly allocated CAFs, which will be scavenged anyway, no need to scavenge SRTs for those. Also, static objects are always evacuated to the oldest gen [2], so any CAFs that are alive but not in the mut_list of the oldest gen will stay alive after a non-major GC, again no need to scavenge SRTs to keep these alive. This also explains why it's OK to not collect static objects (and not treat them as roots) in non-major GCs. However this doesn't explain - Why it's OK to scavenge large objects with scavenge_one(). - Why we scavenge SRTs in non-major collections in other places (e.g. scavenge_block()). Simon, could you say a few words about this? [1]: https://github.com/ghc/ghc/blob/master/rts/sm/Storage.c#L445-L449 [2]: https://github.com/ghc/ghc/blob/master/rts/sm/Scav.c#L1761-L1763 Ömer 2018-03-28 17:49 GMT+03:00 Ben Gamari <[email protected]>: > Hi Simon, > > I'm a bit confused by scavenge_one; namely it doesn't scavenge SRTs. It > appears that it is primarily used for remembered set entries but it's > not at all clear why this means that we can safely ignore SRTs (e.g. in > the FUN and THUNK cases). > > Can you shed some light on this? > > Cheers, > > - Ben > > _______________________________________________ > ghc-devs mailing list > [email protected] > http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs > _______________________________________________ ghc-devs mailing list [email protected] http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
