<div dir="ltr">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).<div><br></div><div>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.</div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Jun 3, 2013 at 1:46 PM, Nathan England <span dir="ltr"><<a href="mailto:nathan@nmecs.com" target="_blank">nathan@nmecs.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">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. </p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">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. </p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">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!</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"> </p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px">Maybe I should have gone with a single 8GB stick of ram instead of dual 4GB. Silly me!</p><span class="HOEnZb"><font color="#888888">
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</font></span><p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"><span class="HOEnZb"><font color="#888888">Nathan</font></span></p><div><div class="h5"><br><br><br><br><br>On Monday, June 03, 2013 13:27:18 Nadim Hoque wrote:<br>
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<p style="margin-top:12px;margin-bottom:0px;margin-left:40px;margin-right:40px;text-indent:0px">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.</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:40px;margin-right:40px;text-indent:0px">On Mon, Jun 3, 2013 at 7:25 AM, Stephen <<a href="mailto:cryptworks@gmail.com" target="_blank"><span style="text-decoration:underline;color:#0057ae">cryptworks@gmail.com</span></a>> wrote:<br>
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<p style="margin-top:12px;margin-bottom:12px;margin-left:45px;margin-right:40px;text-indent:0px">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. </p>
<p style="margin-top:12px;margin-bottom:12px;margin-left:45px;margin-right:40px;text-indent:0px">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.</p>
<p style="margin-top:12px;margin-bottom:12px;margin-left:45px;margin-right:40px;text-indent:0px">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. <br>
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<p style="margin-top:12px;margin-bottom:12px;margin-left:45px;margin-right:40px;text-indent:0px">If you have multiple processors you will want to look for numa. This allows inter processor communication for ram access. </p>
<p style="margin-top:12px;margin-bottom:12px;margin-left:45px;margin-right:40px;text-indent:0px">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.<br>
</p>
<p style="margin-top:0px;margin-bottom:0px;margin-left:45px;margin-right:40px;text-indent:0px">On Mon, Jun 3, 2013 at 6:36 AM, keith smith <<a href="mailto:klsmith2020@yahoo.com" target="_blank"><span style="text-decoration:underline;color:#0057ae">klsmith2020@yahoo.com</span></a>> wrote:<br>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"><br>I found this in an on-line discussion:<br><br>Ganged = dual channel mode for ram. All cores get access to 100% of the ram.<br>
<br>unganged = single channel. Each core gets access to a stick of ram.<br><br>Is this correct?<br><br><br>------------------------<br>Keith Smith<br><br>--- On <span style="font-weight:600">Mon, 6/3/13, Nathan England </span><span style="font-weight:600;font-style:italic"><</span><a href="mailto:nathan@nmecs.com" target="_blank"><span style="font-weight:600;font-style:italic;text-decoration:underline;color:#0057ae">nathan@nmecs.com</span></a><span style="font-weight:600;font-style:italic">></span> wrote:<br>
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<p style="margin-top:12px;margin-bottom:12px;margin-left:5px;margin-right:40px;text-indent:0px"><br>From: Nathan England <<a href="mailto:nathan@nmecs.com" target="_blank"><span style="text-decoration:underline;color:#0057ae">nathan@nmecs.com</span></a>><br>
Subject: Re: AMD vs Intel memory managemement<br>To: "Main PLUG discussion list" <<a href="mailto:plug-discuss@lists.phxlinux.org" target="_blank"><span style="text-decoration:underline;color:#0057ae">plug-discuss@lists.phxlinux.org</span></a>><br>
Date: Monday, June 3, 2013, 1:35 AM</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:5px;margin-right:40px;text-indent:0px">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. </p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:5px;margin-right:40px;text-indent:0px">I love it...</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:5px;margin-right:40px;text-indent:0px"></sarcasm><br><br><br><br><br>On Sunday, June 02, 2013 17:46:19 keith smith wrote:<br></p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:0px;margin-right:0px;text-indent:0px"><br>Hi,<br><br>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.<br>
<br>We had a great thread a while ago the AMD CPU, however I do not think that thread covered memory management.<br><br>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.<br>
<br>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. <br>
<br>Any thoughts on this?<br><br>Thanks!<br><br>------------------------<br>Keith Smith</p></td></tr></tbody></table>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:5px;margin-right:40px;text-indent:0px">Regards,</p>
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<p style="margin-top:0px;margin-bottom:0px;margin-left:5px;margin-right:40px;text-indent:0px">Nathan England</p>
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<a href="http://lists.phxlinux.org/mailman/listinfo/plug-discuss" target="_blank">http://lists.phxlinux.org/mailman/listinfo/plug-discuss</a><br></blockquote></div><br><br clear="all"><div><br></div>-- <br>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.<br>
<br>Stephen
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