Your explanation seems about right to me. The problem though, with a single processor with multiple cores, they are all using the same memory interconnect. While in theory, and quite possibly in true NUMA systems, this is a more efficient way to handle memory management with tasks assigned to a specific processor ( I would imagine this would be huge for VM hosts ) but as far as I know, there are no real world examples or tests that show this actually works any faster with multiple cores. But why does CentOS not register all of my memory? Why less than 3/4 of it? I have actually had my machine swap due to the work load where as if it had access to the other 3 GB of ram it would not have swapped! Maybe I should have gone with a single 8GB stick of ram instead of dual 4GB. Silly me! Nathan On Monday, June 03, 2013 13:27:18 Nadim Hoque wrote: If i recall AMD started doing NUMA which each core gets a dedicated amount of memory that is tied to it. The plus side is that when the core needs something in its own memory region it does not need to put the request in the queue like in non-numa and gets it faster. The down side is if it needs data in a memory region that belongs to another core it will take longer since it essentially has to ask that core for that data. In non-numa architecture the entire memory space is allocated to all cores which means that each core can access memory with out asking another for data. The problem with this is that all memory requests is put in a queue and the core has to wait until the memory controller is able to process the request. For many core and lot of memory systems you are mostly better off with NUMA. Correct me if I am wrong though. On Mon, Jun 3, 2013 at 7:25 AM, Stephen <[email protected][1]> wrote: Not really, Dual channel mode means you can read and write to both Banks of memory at the same time (aka Ganged). Single Channel means you treat all ram as a single bank reading and writing to one and then the other. think Raid 0 vs JBOD if that helps. I personally have had 0 issue with greater than 4 GB of ram in a machine with Linux and a 64 bit kernel. and i have worked with multiple distributions over the years back and forth. the main difference between Intel and AMD i have seen since the core i series CPUs were released is that AMD still has wicked fast memory performance but Intel wins most everything else. If you have multiple processors you will want to look for numa. This allows inter processor communication for ram access. It should not matter if you are running ganged or unchanged your is should see all ram installed with the exception of the PCI/pcie/chip set nibbling 100 to 700mb for doing its thing in consumer chipsets. On Mon, Jun 3, 2013 at 6:36 AM, keith smith <[email protected][2]> wrote: *Mon, 6/3/13, Nathan England /<[email protected][3]>/* wrote: [email protected]_>Subject: Re: AMD vs Intel memory managemementTo: "Main PLUG discussion list" <[email protected][4]>Date: Monday, June 3, 2013, 1:35 AM Yeah, it's a wonderful thing AMD calls "unganged" mode. I have 8 GB of ram in my server and the motherboard has enabled "unganged" mode to be more efficient. CentOS only recognizes 5.8 GB of ram and I cannot turn off unganged mode. I love it... </sarcasm> On Sunday, June 02, 2013 17:46:19 keith smith wrote: -- Regards, Nathan England ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NME Computer Services http://www.nmecs.com[5] Nathan England ([email protected][3]) Systems Administration / Web Application Development Information Security Consulting (480) 559.9681[6] -----Inline Attachment Follows----- ---------------------------------------------------PLUG-discuss mailing list - PLUG- [email protected][7] http://lists.phxlinux.org/mailman/listinfo/plug-discuss[8] [email protected][9] http://lists.phxlinux.org/mailman/listinfo/plug-discuss[8] -- A mouse trap, placed on top of your alarm clock, will prevent you from rolling over and going back to sleep after you hit the snooze button.
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