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. :-(
There are two underlying causes. First, the size of the kmem map, which
holds the kernel's heap, is recorded in a 32-bit int. So, setting
vm.kmem_size to 4100M is leading to integer overflow. The following
change addresses this issue:
sys/kern/kern_malloc.c
Revision *1.167*: download
<http://www.freebsd.org/cgi/cvsweb.cgi/%7Echeckout%7E/src/sys/kern/kern_malloc.c?rev=1.167;content-type=text%2Fplain>
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/Sat Jul 5 19:34:33 2008 UTC/ (2 months ago) by /alc/
Branches: MAIN
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CVS tags: HEAD
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Diff to: previous 1.166: preferred
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colored
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Changes since revision 1.166: +11 -11 lines
SVN rev 180308 on 2008-07-05 19:34:33Z by alc
Enable the creation of a kmem map larger than 4GB.
Submitted by: Tz-Huan Huang
Make several variables related to kmem map auto-sizing static.
Found by: CScout
Second, there is no room for a kmem map greater than 4GB unless the
overall KVM size is greater than 6GB. Specifically, a >4GB kmem map
isn't possible with 6GB KVM because the kmem map would overlap the
kernel's code, data, and bss segment.
If you're able to apply the above kern_malloc.c change to your kernel,
then I should be able to describe how to increase your KVM beyond 6GB.
Regards,
Alan
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