Increasing KVM on amd64

Jeremy Chadwick koitsu at
Thu Sep 11 04:28:03 UTC 2008

On Wed, Sep 10, 2008 at 04:12:25PM -0700, Artem Belevich wrote:
> Alan,
> Thanks a lot for the patch. I've applied it to RELENG_7 and it seems
> to work great - "make -j8 buildworld" succeeds, linux emulation seems
> to work well enough to run linux-sun-jdk14 binaries, ZFS ARC size is
> bigger, too. So far I didn't see any ZFS-related KVM shortages either.
> The only problem is that everything is fine as long as vm.kmem_size is
> set to less or equal to 4096M. As soon as I set it to 4100M or
> anything larger, kernel crashes on startup. I'm unable to capture
> exact crash messages as they keep scrolling really fast on the screen
> for a few seconds until the box reboots. Unfortunately  the box does
> not have built-in serial ports, so the messages are gone before I can
> see them. :-(
> Is there a way to bump up KVM size even further - beyond 6GB? I've got
> a box with 8GB or RAM and would like let ZFS ARC use most of it which
> would require pretty large vm.kmem_max to fit it in.

I was told fairly recently (a few days ago) that the 6GB limit was
increased to 512GB on HEAD/CURRENT.  The 6GB limit was during a
"transitional" phase of addressing the problem.

| Jeremy Chadwick                                jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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