Does Cyrus benefit greatly from increased FS buffer cache?

[David Lang]

On Thu, 16 Apr 2009, Sebastian Hagedorn wrote:

> --On 16. April 2009 10:58:15 +1000 Rob Mueller <robm at fastmail.fm> 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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