kmem_map too small

Andrew Kolchoogin andrew at
Fri Nov 16 00:39:36 PST 2007

В Пт, 16/11/2007 в 09:16 +0100, Kris Kennaway пишет:

> Check the archives, this comes up a lot (you need to increase the amount 
> of memory allocated to the kernel).
    Already did.

    The question actually is how much memory I should allocate for
kernel (exactly, what numbers should be placed into /boot/loader.conf in
vm.kmem_size and vm.kmem_size_max) and what amount of kernel memory
depends on and how I could calculate kernel memory needs.

    Trivial answer "just try to experiment" is not definitely enough. :)

First of all, this process can be _extremely_ lengthy: about two months
ago I have tried to "brute force" guess vm.kmem* values to start using
ZFS on my desktop at work: two weeks for testing is very large amount of
time, and, as said by Dijkstra, "testing can only show us presence of
bugs, and not their absence": "cvs -z 5 -g up -P -d" done in /usr/ports
(very good test to crash your machine if you're using ZFS because of
heavy usage of ZFS POSIX name resolution cache) stopped crashing my box,
but I can't say that any other test will not crash it.

Second, the machine in question operates unattended, and our technical
support engineers are not qualified enough to tweak boot loader
parameters, as such, I should constantly monitor this server what I
don't wish to do. :)
    С уважением,
        Андрей Кольчугин.

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