Re: Does Cyrus benefit greatly from increased FS buffer cache?

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On Thu, 16 Apr 2009, Sebastian Hagedorn wrote:

--On 16. April 2009 10:58:15 +1000 Rob Mueller <robm@xxxxxxxxxxx> wrote:

http://blog.fastmail.fm/2007/09/21/reiserfs-bugs-32-bit-vs-64-bit-kernel
s-cache-vs-inode-memory/

Anyone have any specific thoughts?  Is there any other benefit we might
see from large memory allocation in 64-bit architecture?

Given that I wrote that blog post, I can only tell you that in our
environment, 64-bit kernels made a big difference.

I wonder if ext3 behaves differently, Red Hat's 32-bit behaves differently,
or if something altogether different is going on. We are currently running
RHEL 3 in 32-bit mode, our servers have 16 GB, and most of it is used for
caching:

# free
            total       used       free     shared    buffers     cached
Mem:      16214344   16197612      16732          0      86944   13415172
-/+ buffers/cache:    2695496   13518848
Swap:      4192944       8436    4184508

So it would seem that a 64-bit kernel wouldn't improve on that, right? Or
is that a difference between 2.4 and 2.6?

64 bit kernels will be significantly more efficiant, and more reliable with that much memory.

in addition, in 64 bit mode the system is able to use twice as many registers on the CPU, which can frequently be a significant win in and of itself (even on machines with 1G of ram)

I've run both kernels on the same system and always have found that the 64 bit kernel is an advantage.

I tend to do the same thing for userspace (unless I am running something that doesn't work with 64 bit userspace), but there the benifit is more hit-and-miss

David Lang

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