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OpenBSD/amd64: BIGMEM is default

Posted 04-05-2011 at 09:26 AM by rocket357
Updated 04-05-2011 at 09:47 PM by rocket357

Thanks to the work of Bob Beck and countless other OpenBSD developers, amd64 BIGMEM is now turned on by default in the April 4th snapshot of OpenBSD-CURRENT.

OpenBSD 4.9-current (GENERIC.MP) #865: Mon Apr  4 13:03:14 MDT 2011
real mem = 137428045824 (131061MB)
avail mem = 133755703296 (127559MB)
mainbus0 at root
bios0 at mainbus0: SMBIOS rev. 2.6 @ 0xdf79c000 (103 entries)
bios0: vendor Dell Inc. version "1.1.9" date 05/21/2010
bios0: Dell Inc. PowerEdge R715
This is exciting news, perhaps I can run a true PostgreSQL OS benchmark to see what kind of performance I can expect on Linux, FreeBSD, and OpenBSD.

Edit - if you have access to an amd64 machine with over 4 GB of RAM, please test this (or any later) snapshot and report any bugs you find. It would be a shame if BIGMEM got pulled again for unresolved bugs.
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  1. Old Comment
    Why not run a 64bit OS/Kernel if you have an amd64? Other than a few commercial pieces of software, there isn't really a need to run 32bit any more.
    Posted 04-06-2011 at 09:55 PM by lumak lumak is offline
  2. Old Comment
    It *IS* 64 bit, lumak. The problem is that many MMU's on amd64 are buggy (this problem doesn't exist for sparc64 or many other architectures), and rather than say "we won't support motherboards that don't have these chipsets", they left BIGMEM (over 4 GB) support turned off for OpenBSD amd64. Other OS's obviously have their own implementations of BIGMEM (64-bit address space), so that's entirely different.

    Now that the vast majority of these buggy MMU's are getting old and being phased out, and the OpenBSD team has rewritten their own implementation of BIGMEM, it's being considered for a permanent spot in the OpenBSD 5.0 release. (I have a non-buggy MMU on an HP Proliant machine that runs OpenBSD-CURRENT, and it has BIGMEM enabled because I turned it on manually, and it hasn't had any problems).

    This is mostly a hardware issue, not a 32/64 bit or even software issue. (Thought, I suppose at the core of it, this really is an "OpenBSD team" issue, since they absolutely will not allow crap code into OpenBSD-RELEASE.)
    Posted 04-07-2011 at 08:43 AM by rocket357 rocket357 is offline
    Updated 04-07-2011 at 08:45 AM by rocket357
  3. Old Comment
    err yeah BSD.. Figured that since it's a non issue for 64bit linux kernel that BSD would be the same.
    Posted 04-07-2011 at 11:10 PM by lumak lumak is offline
  4. Old Comment
    It is a non-issue for NetBSD/FreeBSD/etc... it was only an issue for OpenBSD. (and hopefully this implementation won't run into problems like the last one and won't get yanked the same way).
    Posted 04-08-2011 at 07:07 AM by rocket357 rocket357 is offline


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