[GHC] #9706: New block-structured heap organization for 64-bit

[GHC]

#9706: New block-structured heap organization for 64-bit
-------------------------------------+-------------------------------------
              Reporter:  ezyang      |            Owner:  simonmar
                  Type:  task        |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Runtime     |          Version:  7.8.3
  System                             |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------

Comment (by rwbarton):

 I did my experiments on a Linux system with overcommit disabled and
 watched the `Committed_AS` number from `/proc/meminfo`. According to my
 tests, anonymous pages which have never been mapped with `PROT_WRITE`
 don't count against the commit limit. Once a page is given `PROT_WRITE`
 permissions then it counts as committed even if `PROT_WRITE` is removed
 before the page is ever touched.

 I would guess we can "un-commit" pages by doing a new mmap over them with
 `PROT_NONE`, but I didn't test this.

 Carter tested that on OS X, mmapping 100 TB doesn't take any noticeable
 time, at least.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9706#comment:14>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler