I have not run CentOS on my current system, but ununtu 13.04 ran like a champ until i broke it. all 16 GB (2x8 set up as dual channel). I can try to install Cent and see what it tells me. it may be that there is a kernel param that is not lined up right. On Mon, Jun 3, 2013 at 1:46 PM, Nathan England wrote: > ** > > > > > > 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 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 wrote: > > > > > I found this in an on-line discussion: > > Ganged = dual channel mode for ram. All cores get access to 100% of the > ram. > > unganged = single channel. Each core gets access to a stick of ram. > > Is this correct? > > > ------------------------ > Keith Smith > > --- On Mon, 6/3/13, Nathan England wrote: > > > From: Nathan England > Subject: Re: AMD vs Intel memory managemement > To: "Main PLUG discussion list" > 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... > > > > > > > > > On Sunday, June 02, 2013 17:46:19 keith smith wrote: > > > > > Hi, > > After that great thread on 32bit vs 64bit, I was wondering if it would be > beneficial at this point to drill down to the CPU level : AMD vs Intel. > > We had a great thread a while ago the AMD CPU, however I do not think that > thread covered memory management. > > I almost went for an AMD CPU this go around (I have a couple from prior > purchases), however after hearing that AMD does some weird memory > management at the core level, assigning memory by the bank to each core, I > thought I would go with an Intel CPU. > > If I understand this correctly, It sounds like under some or most > circumstances the server will lose a portion of the total memory because > under AMD RAM is assigned at the core level and bank level. I assume Intel > uses memory as a pool. Need memory just grab some until it is gone. > > Any thoughts on this? > > Thanks! > > ------------------------ > Keith Smith > > > > -- > > > > > > > > Regards, > > > > Nathan England > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > NME Computer Services http://www.nmecs.com > > Nathan England (nathan@nmecs.com) > > Systems Administration / Web Application Development > > Information Security Consulting > > (480) 559.9681 > > > > > -----Inline Attachment Follows----- > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > > > > > -- > 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. > > Stephen > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > > > > > -- > > Nadim Hoque > Systems Support Analyst > Engineering Technical Services > Arizona State University > Cell: 480-518-6235 > > > > -- > > > > > > > > Regards, > > > > Nathan England > > > > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > NME Computer Services http://www.nmecs.com > > Nathan England (nathan@nmecs.com) > > Systems Administration / Web Application Development > > Information Security Consulting > > (480) 559.9681 > > > > --------------------------------------------------- > PLUG-discuss mailing list - PLUG-discuss@lists.phxlinux.org > To subscribe, unsubscribe, or to change your mail settings: > http://lists.phxlinux.org/mailman/listinfo/plug-discuss > -- 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. Stephen