Short course: a replacement for malloc for use in contexts that can't "move memory" after an address is passed out, but want/need the benefits of compactification anyway.
Key idea: if the allocator dedicates each OS page to requests of a specific class, then consider two pages devoted to the same class, where `-` is free space, and X and Y are allocated chunks: page1: X--XX-X---X page2: --Y--Y--YY- Because there's no overlap in the offsets of allocated blocks here, we can copy the 4 Ys into page1 (or Xs into page2). Then tell the OS to change its page tables so that the virtual addresses of page1 amd page2 _both_ map to the physical page page1 referred to. page2's physical page can be returned to the OS then. No _virtual_ address malloc ever handed out needs to change. The rest is making this all safe & "go fast". On Sat, Sep 28, 2019 at 2:06 PM MRAB <pyt...@mrabarnett.plus.com> wrote: > > Here's a video about memory fragmentation and compaction that you might > find interesting: > > "Compacting the Uncompactable" by Bobby Powers > https://www.youtube.com/watch?v=c1UBJbfR-H0 > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/G6OR45TETKIFZDVWAK5ZGLLFTIC422TG/ _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-le...@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/VMP5RXVQV574SXNJC5SNIJNAL3PYZZC6/
