bigmem vs 64bit kernel

austinium · 03-30-2011, 07:19 AM

hi,

I currently have a 32bit system running tomcat, it has 2GB of RAM, i will be upgrading to 4GB(max the mobo will support), i am trying the weight the pros & cons of using a bigmem kernel instead of doing a fresh 64bit install.

How do the two compare? (i don't really have any issues doing a fresh 64bit install, but if the using bigmem kernel is just as good then there is no point doing a fresh 64bit install).

Thanks,

Noway2 · 03-30-2011, 07:45 AM

Just to point that you may already know, a 32 bit kernel will handle up to 4GB of memory. I don't have an answer for you on the differences between the two kernels, so I can't speak for whether or not one would have a performance advantage over the other. I thought I would mention that it isn't necessary to change your kernel for 4GB of memory, just in case that was a possible consideration for you.

TobiSGD · 03-30-2011, 07:59 AM

Quote:

Originally Posted by Noway2

Just to point that you may already know, a 32 bit kernel will handle up to 4GB of memory. I don't have an answer for you on the differences between the two kernels, so I can't speak for whether or not one would have a performance advantage over the other. I thought I would mention that it isn't necessary to change your kernel for 4GB of memory, just in case that was a possible consideration for you.

In theory, a 32 bit kernel would support 4GB of memory, but in practice it will not, at least on systems with x86-architecture. The add-in cards in the system will use the memory below 4GB to map there own memory and I/O there. That address space is not usable for the system. A 32 bit PAE-kernel or a 64 bit kernel is able to use that memory with a simple trick, the space blocked by the peripheral devices is remapped to an address space above 4GB. A 32 bit kernel without PAE is not able to use that, just because it is above the 4GB limit.

austinium · 03-30-2011, 11:14 PM

thanks for the replies ppl

would there be performance hit if i were to use a 32bit PAE/Bigmem kernel instead of a 64bit one???
this may be a n00b-ish question but would the device drivers for a regular 32bit kernel also work for a 32bit PAE/bigmem kernel???

Reuti · 03-31-2011, 06:10 AM

I would go for 64 bit anyway, if the CPU is capable of it: http://en.wikipedia.org/wiki/64-bit#Pros_and_cons

TobiSGD · 03-31-2011, 07:42 AM

Quote:

Originally Posted by austinium

thanks for the replies ppl

would there be performance hit if i were to use a 32bit PAE/Bigmem kernel instead of a 64bit one???
this may be a n00b-ish question but would the device drivers for a regular 32bit kernel also work for a 32bit PAE/bigmem kernel???

The performance loss with a PAE-kernel is minimal. Regarding the drivers, it depends. The more common drivers, like the ATI or NVidia drivers for video-cards work fine. If you have to use more exotic ones, you have to try it.
Bas as recommended before, 64 bit is mature enough (at least I have no problems with that), so go for 64 bit.