On Tue, Aug 9, 2022, 8:36 AM Po Lu wrote: > Lynn Winebarger writes: > > > The second statement was comparing dumped versus undumped performance, > > whether native- or byte- compiled. This isn't a novel observation, > > but the dump is basically a one-shot mark-compact GC collection, and > > the mmap'ed pdump files would ideally be treated like the old > > generation of a generational collector, and so not traced in most (or > > all) collection cycles. This is (or should be) one benefit of pure > > space, although the requirement that it be read-only could be dropped > > as long as the write-barrier remains and is used to record any > > inter-generational pointers to a root set traced by the collector. > > This (very) minor benefit of pure space is already gone, since it is > unprotected and scanned normally for garbage collection in pdumper > builds. > I'm not sure you can conclude that the benefit would be minor when the non-collected space is a 184MB dump file instead of a fixed pure space that is 2 or 2.4MB as it is in the standard pdump. At least some vestiges of the write barrier appear to be in place during dump mode. I've had to make a lot of minor corrections of "defconst" keymaps to defvar, for example due to pure_write_error getting called. Whether that barrier is uniformly enforced or not is one of the reasons I suspect this quick hack would not be sufficient. Lynn