Dear Dave, >> On my large machine, 'free' fails to show about 2GB memory ... > You probably have a memory hole. ... > The e820 map (during early boot in dmesg) or /proc/iomem will let you > locate your memory holes. Now that my machine is running an amd64 kernel, 'free' shows total Mem 65854128 (up from 64447796 with PAE kernel), and I do not see much change in /proc/iomem output (below). Is that as should be? Thanks, Paul Paul Szabo psz@xxxxxxxxxxxxxxxxx http://www.maths.usyd.edu.au/u/psz/ School of Mathematics and Statistics University of Sydney Australia --- root@zeno:~# uname -a Linux zeno.maths.usyd.edu.au 3.2.35-pk06.12-amd64 #2 SMP Thu Jan 17 13:19:53 EST 2013 x86_64 GNU/Linux root@zeno:~# free total used free shared buffers cached Mem: 65854128 1591704 64262424 0 227036 175620 -/+ buffers/cache: 1189048 64665080 Swap: 195312636 0 195312636 root@zeno:~# cat /proc/iomem 00000000-0000ffff : reserved 00010000-00099bff : System RAM 00099c00-0009ffff : reserved 000a0000-000bffff : PCI Bus 0000:00 000c0000-000dffff : PCI Bus 0000:00 000c0000-000c7fff : Video ROM 000c8000-000cf5ff : Adapter ROM 000cf800-000d07ff : Adapter ROM 000d0800-000d0bff : Adapter ROM 000e0000-000fffff : reserved 000f0000-000fffff : System ROM 00100000-7e445fff : System RAM 01000000-0168f8c6 : Kernel code 0168f8c7-018f24bf : Kernel data 0197d000-019dafff : Kernel bss 7e446000-7e565fff : ACPI Non-volatile Storage 7e566000-7f1e2fff : reserved 7f1e3000-7f25efff : ACPI Tables 7f25f000-7f31cfff : reserved 7f31d000-7f323fff : ACPI Non-volatile Storage 7f324000-7f333fff : reserved 7f334000-7f33bfff : ACPI Non-volatile Storage 7f33c000-7f365fff : reserved 7f366000-7f7fffff : ACPI Non-volatile Storage 7f800000-7fffffff : RAM buffer 80000000-dfffffff : PCI Bus 0000:00 80000000-8fffffff : PCI MMCONFIG 0000 [bus 00-ff] 80000000-8fffffff : reserved 90000000-9000000f : 0000:00:16.0 90000010-9000001f : 0000:00:16.1 dd000000-ddffffff : PCI Bus 0000:08 dd000000-ddffffff : 0000:08:03.0 de000000-de4fffff : PCI Bus 0000:07 de000000-de3fffff : 0000:07:00.0 de47c000-de47ffff : 0000:07:00.0 de600000-de6fffff : PCI Bus 0000:02 df000000-df8fffff : PCI Bus 0000:08 df000000-df7fffff : 0000:08:03.0 df800000-df803fff : 0000:08:03.0 df900000-df9fffff : PCI Bus 0000:07 dfa00000-dfafffff : PCI Bus 0000:02 dfa00000-dfa1ffff : 0000:02:00.1 dfa00000-dfa1ffff : igb dfa20000-dfa3ffff : 0000:02:00.0 dfa20000-dfa3ffff : igb dfa40000-dfa43fff : 0000:02:00.1 dfa40000-dfa43fff : igb dfa44000-dfa47fff : 0000:02:00.0 dfa44000-dfa47fff : igb dfb00000-dfb03fff : 0000:00:04.7 dfb04000-dfb07fff : 0000:00:04.6 dfb08000-dfb0bfff : 0000:00:04.5 dfb0c000-dfb0ffff : 0000:00:04.4 dfb10000-dfb13fff : 0000:00:04.3 dfb14000-dfb17fff : 0000:00:04.2 dfb18000-dfb1bfff : 0000:00:04.1 dfb1c000-dfb1ffff : 0000:00:04.0 dfb20000-dfb200ff : 0000:00:1f.3 dfb21000-dfb217ff : 0000:00:1f.2 dfb21000-dfb217ff : ahci dfb22000-dfb223ff : 0000:00:1d.0 dfb22000-dfb223ff : ehci_hcd dfb23000-dfb233ff : 0000:00:1a.0 dfb23000-dfb233ff : ehci_hcd dfb25000-dfb25fff : 0000:00:05.4 dfffc000-dfffdfff : pnp 00:02 e0000000-fbffffff : PCI Bus 0000:80 fbe00000-fbefffff : PCI Bus 0000:84 fbe00000-fbe3ffff : 0000:84:00.0 fbe40000-fbe5ffff : 0000:84:00.0 fbe60000-fbe63fff : 0000:84:00.0 fbf00000-fbf03fff : 0000:80:04.7 fbf04000-fbf07fff : 0000:80:04.6 fbf08000-fbf0bfff : 0000:80:04.5 fbf0c000-fbf0ffff : 0000:80:04.4 fbf10000-fbf13fff : 0000:80:04.3 fbf14000-fbf17fff : 0000:80:04.2 fbf18000-fbf1bfff : 0000:80:04.1 fbf1c000-fbf1ffff : 0000:80:04.0 fbf20000-fbf20fff : 0000:80:05.4 fbffe000-fbffffff : pnp 00:12 fc000000-fcffffff : pnp 00:01 fd000000-fdffffff : pnp 00:01 fe000000-feafffff : pnp 00:01 feb00000-febfffff : pnp 00:01 fec00000-fec003ff : IOAPIC 0 fec01000-fec013ff : IOAPIC 1 fec40000-fec403ff : IOAPIC 2 fed00000-fed003ff : HPET 0 fed08000-fed08fff : pnp 00:0c fed1c000-fed3ffff : reserved fed1c000-fed1ffff : pnp 00:0c fed45000-fedfffff : pnp 00:01 fee00000-fee00fff : Local APIC ff000000-ffffffff : reserved ff000000-ffffffff : pnp 00:0c 100000000-107fffffff : System RAM root@zeno:~# --- For comparison, output obtained (and reported previously) when machine was running PAE kernel: root@zeno:~# cat /proc/iomem 00000000-0000ffff : reserved 00010000-00099bff : System RAM 00099c00-0009ffff : reserved 000a0000-000bffff : PCI Bus 0000:00 000a0000-000bffff : Video RAM area 000c0000-000dffff : PCI Bus 0000:00 000c0000-000c7fff : Video ROM 000c8000-000cf5ff : Adapter ROM 000cf800-000d07ff : Adapter ROM 000d0800-000d0bff : Adapter ROM 000e0000-000fffff : reserved 000f0000-000fffff : System ROM 00100000-7e445fff : System RAM 01000000-01610e15 : Kernel code 01610e16-01802dff : Kernel data 01880000-018b2fff : Kernel bss 7e446000-7e565fff : ACPI Non-volatile Storage 7e566000-7f1e2fff : reserved 7f1e3000-7f25efff : ACPI Tables 7f25f000-7f31cfff : reserved 7f31d000-7f323fff : ACPI Non-volatile Storage 7f324000-7f333fff : reserved 7f334000-7f33bfff : ACPI Non-volatile Storage 7f33c000-7f365fff : reserved 7f366000-7f7fffff : ACPI Non-volatile Storage 7f800000-7fffffff : RAM buffer 80000000-dfffffff : PCI Bus 0000:00 80000000-8fffffff : PCI MMCONFIG 0000 [bus 00-ff] 80000000-8fffffff : reserved 90000000-9000000f : 0000:00:16.0 90000010-9000001f : 0000:00:16.1 dd000000-ddffffff : PCI Bus 0000:08 dd000000-ddffffff : 0000:08:03.0 de000000-de4fffff : PCI Bus 0000:07 de000000-de3fffff : 0000:07:00.0 de47c000-de47ffff : 0000:07:00.0 de600000-de6fffff : PCI Bus 0000:02 df000000-df8fffff : PCI Bus 0000:08 df000000-df7fffff : 0000:08:03.0 df800000-df803fff : 0000:08:03.0 df900000-df9fffff : PCI Bus 0000:07 dfa00000-dfafffff : PCI Bus 0000:02 dfa00000-dfa1ffff : 0000:02:00.1 dfa00000-dfa1ffff : igb dfa20000-dfa3ffff : 0000:02:00.0 dfa20000-dfa3ffff : igb dfa40000-dfa43fff : 0000:02:00.1 dfa40000-dfa43fff : igb dfa44000-dfa47fff : 0000:02:00.0 dfa44000-dfa47fff : igb dfb00000-dfb03fff : 0000:00:04.7 dfb04000-dfb07fff : 0000:00:04.6 dfb08000-dfb0bfff : 0000:00:04.5 dfb0c000-dfb0ffff : 0000:00:04.4 dfb10000-dfb13fff : 0000:00:04.3 dfb14000-dfb17fff : 0000:00:04.2 dfb18000-dfb1bfff : 0000:00:04.1 dfb1c000-dfb1ffff : 0000:00:04.0 dfb20000-dfb200ff : 0000:00:1f.3 dfb21000-dfb217ff : 0000:00:1f.2 dfb21000-dfb217ff : ahci dfb22000-dfb223ff : 0000:00:1d.0 dfb22000-dfb223ff : ehci_hcd dfb23000-dfb233ff : 0000:00:1a.0 dfb23000-dfb233ff : ehci_hcd dfb25000-dfb25fff : 0000:00:05.4 dfffc000-dfffdfff : pnp 00:02 e0000000-fbffffff : PCI Bus 0000:80 fbe00000-fbefffff : PCI Bus 0000:84 fbe00000-fbe3ffff : 0000:84:00.0 fbe40000-fbe5ffff : 0000:84:00.0 fbe60000-fbe63fff : 0000:84:00.0 fbf00000-fbf03fff : 0000:80:04.7 fbf04000-fbf07fff : 0000:80:04.6 fbf08000-fbf0bfff : 0000:80:04.5 fbf0c000-fbf0ffff : 0000:80:04.4 fbf10000-fbf13fff : 0000:80:04.3 fbf14000-fbf17fff : 0000:80:04.2 fbf18000-fbf1bfff : 0000:80:04.1 fbf1c000-fbf1ffff : 0000:80:04.0 fbf20000-fbf20fff : 0000:80:05.4 fbffe000-fbffffff : pnp 00:12 fc000000-fcffffff : pnp 00:01 fd000000-fdffffff : pnp 00:01 fe000000-feafffff : pnp 00:01 feb00000-febfffff : pnp 00:01 fec00000-fec003ff : IOAPIC 0 fec01000-fec013ff : IOAPIC 1 fec40000-fec403ff : IOAPIC 2 fed00000-fed003ff : HPET 0 fed08000-fed08fff : pnp 00:0c fed1c000-fed3ffff : reserved fed1c000-fed1ffff : pnp 00:0c fed45000-fedfffff : pnp 00:01 fee00000-fee00fff : Local APIC ff000000-ffffffff : reserved ff000000-ffffffff : pnp 00:0c 100000000-107fffffff : System RAM root@zeno:~# -- To 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