I'm planning for new Centos 4 computers using the 64bit distribution and is wondering if there is a difference on how much RAM memory you should use on a 32bit versus 64bit operating system?
Will processes such as for example KDE, Firefox use more memory on the 64bit architecture than on the 32bit and if so by how much as a rule of thumb?
Kind regards, Christian
On 8/28/06, Christian Nygaard christiannygaard@gmail.com wrote:
I'm planning for new Centos 4 computers using the 64bit distribution and is wondering if there is a difference on how much RAM memory you should use on a 32bit versus 64bit operating system?
Will processes such as for example KDE, Firefox use more memory on the 64bit architecture than on the 32bit and if so by how much as a rule of thumb?
I don't think so, at least as I understand things 64 bit just means you can use more memory not that you must. I don't know enough about it but it seems to me you will gain some size from the fact that pointers/addresses are now 8 bytes instead of 4, but I would think that would not be that big of a deal.
Cheers...james
Christian Nygaard wrote:
I'm planning for new Centos 4 computers using the 64bit distribution and is wondering if there is a difference on how much RAM memory you should use on a 32bit versus 64bit operating system?
there is no difference in how much RAM memory you should use but if you are going to get a box with more than 1GB of RAM (I think it is 1G...) using AMD's (note Intel: EMT64 cpus don't count) cpus will give you better memory performance.
Christian Nygaard wrote:
I'm planning for new Centos 4 computers using the 64bit distribution and is wondering if there is a difference on how much RAM memory you should use on a 32bit versus 64bit operating system?
Yes. Several low-limits are higher on 64-bit than on 32-bit, like minimum for Gnome install is 128MB on 32-bit and 256MB on 64-bit. I assume you would have more memory than that anyway. 64-bit will use more memory, how much depends. If you add 20% to what you need on 32-bit you should generally be safe. What kind of system are you considering 64-bit on?
Feizhou wrote:
there is no difference in how much RAM memory you should use but if you are going to get a box with more than 1GB of RAM (I think it is 1G...) using AMD's (note Intel: EMT64 cpus don't count) cpus will give you better memory performance.
You really like broad, general statements with your personal opinion, right? :)
AMD's on-chip memory controller gives it lower latency, no matter how much memory you have installed. Memory DIMM mix for Dual Channel can give bandwidht improvements, but both for Intel and AMD architectures. Yes, there are minute differences in how EMT64 and AMD64 chips handles page tables and addressable memory but for all practical intents and purposes they are the same.
Feizhou wrote:
there is no difference in how much RAM memory you should use but if you are going to get a box with more than 1GB of RAM (I think it is 1G...) using AMD's (note Intel: EMT64 cpus don't count) cpus will give you better memory performance.
You really like broad, general statements with your personal opinion, right? :)
=P
AMD's on-chip memory controller gives it lower latency, no matter how much memory you have installed. Memory DIMM mix for Dual Channel can give bandwidht improvements, but both for Intel and AMD architectures. Yes, there are minute differences in how EMT64 and AMD64 chips handles page tables and addressable memory but for all practical intents and purposes they are the same.
Hmm, well, Intel's implementation of AMD's 64-bit instructions is not exactly the same. As you have said, those 'minute' differences with regard to memory addressing will not cause software problems but the kernel will handle memory access differently when more than 1GB of RAM is installed and on an AMD cpu, the kernel uses a more efficient method.
On 8/29/06, Morten Torstensen morten@mortent.org wrote:
Christian Nygaard wrote:
I'm planning for new Centos 4 computers using the 64bit distribution and is wondering if there is a difference on how much RAM memory you should use on a 32bit versus 64bit operating system?
Yes. Several low-limits are higher on 64-bit than on 32-bit, like minimum for Gnome install is 128MB on 32-bit and 256MB on 64-bit. I assume you would have more memory than that anyway. 64-bit will use more memory, how much depends. If you add 20% to what you need on 32-bit you should generally be safe. What kind of system are you considering 64-bit on?
Thanks for this input regarding Gnome memory usage it is insightful and the percentage rule of thumb. The system will be 1U Dual Woodcrest 5140 terminal server and have somewhere around 8GB of memory (thats amount is undecided depending on input from this thread) and it will run around 40 KDE desktops. Of the memory I probably need to reserve around 2GB for virtual Windows 2000 server dozers and reserve io ops for sporadic reboots of the latter. Its currently handling somewhat ok with 6GB of memory on two 32bit Dual Xeon machines for the same user load.
Cheers, Chris
Christian Nygaard wrote:
Thanks for this input regarding Gnome memory usage it is insightful and the percentage rule of thumb. The system will be 1U Dual Woodcrest 5140 terminal server and have somewhere around 8GB of memory
The sweet spot for memory size is around 10GB for a hugemem 32-bit kernel. At 16GB or more, I would definitively go for a 64-bit kernel if possible.
reserve io ops for sporadic reboots of the latter. Its currently handling somewhat ok with 6GB of memory on two 32bit Dual Xeon machines for the same user load.
So both machines have 6GB, or 2x3GB?
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Christian Nygaard -
Feizhou -
James Olin Oden -
Morten Torstensen