LARGE single-system Cyrus installs?

[David Lang]

On Tue, 9 Oct 2007, Andrew Morgan wrote:

> On Sat, 6 Oct 2007, Rob Mueller wrote:
>
>> As it turns out, the memory leaks weren't critical, because the the pages do
>> seem to be reclaimed when needed, though it was annoying not knowing exactly
>> how much memory was really free/used. The biggest problem was that with
>> cyrus you have millions of small files, and with a 32bit linux kernel the
>> inode cache has to be in low memory, severely limiting how many files the OS
>> will cache.
>>
>> See this blog post for the gory details, and why a 64-bit kernel was a nice
>> win for us.
>>
>> http://blog.fastmail.fm/2007/09/21/reiserfs-bugs-32-bit-vs-64-bit-kernels-cache-vs-inode-memory/
>
> Yesterday I checked my own Cyrus servers to see if I was running out of
> lowmem, and it sure looked like it.  Lowmem had only a couple MB free, and
> I had 2GB of free memory that was not being used for cache.
>
> I checked again today and everything seems to be fine - 150MB of lowmem
> free and almost no free memory (3GB cached)!  Grrr.
>
> Anyways, I was looking into building a 64-bit kernel.  I'm running Debian
> Sarge (I know, old) on a Dell 2850 with Intel Xeon (Nocona) CPUs and 4GB
> RAM.  My kernel version is 2.6.14.5, built from kernel.org sources.  It
> has "High Memory Support (64GB)" selected.
>
> When I run menuconfig, I'm not seeing any obvious place to switch from
> 32-bit to 64-bit.  Could you elaborate a bit about how you switched to a
> 64-bit kernel?  Also, are you running a full 64-bit distro, or just a
> 64-bit kernel?

you need a full 64 bit toolchain to compile a 64 bit kernel, the easy way to do 
this is to compile the kernel on a 64 bit distro.

if you have the toolchain you can add arch=x86_64 to your make command

if you are not converting everything over to 64 bit remember to enable 32 bit 
userspace (cyrus won't take advantage of all the ram, but the kernel will, so 
it's definantly still a win)

with some older versions of the iptables binaries you can run into trouble with 
a 64 bit kernel and 32 bit userspace. unless you take the time to make sure that 
you aren't running versions that have this problem don't execute any iptables 
commands when running in mixed mode.

David Lang