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On 08/10/2013 19:04, Alexander Kapshuk wrote: |
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> On 10/07/2013 10:42 PM, Alan McKinnon wrote: |
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>> On 07/10/2013 21:28, Alexander Kapshuk wrote: |
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>>> Is the message below I should do something about? |
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>>> |
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>>> box0=; dmesg|grep -i PAE |
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>>> [ 0.000000] Notice: NX (Execute Disable) protection cannot be |
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>>> enabled: non-PAE kernel! |
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>>> |
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>>> |
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>>> My CPU seems to have support for it. |
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>>> box0=; grep pae /proc/cpuinfo |
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>>> flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca |
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>>> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm |
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>>> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl |
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>>> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm |
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>>> flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca |
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>>> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm |
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>>> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl |
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>>> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm |
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>>> |
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>>> But not my kernel, as far as I can tell. |
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>>> box0=; uname -a |
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>>> Linux box0 3.10.7-gentoo-r1 #1 SMP Sat Oct 5 23:57:58 EEST 2013 i686 |
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>>> Intel(R) Pentium(R) Dual CPU T3400 @ 2.16GHz GenuineIntel GNU/Linux |
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>>> |
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>>> box0=; grep -i pae .config |
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>>> box0=; echo $? |
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>>> 1 |
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>>> |
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>>> Thanks. |
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>>> |
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>>> |
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>> |
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>> Symbol: ARM_LPAE [=ARM_LPAE] |
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>> Type : unknown |
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>> |
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>> Symbol: X86_PAE [=n] |
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>> Type : boolean |
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>> Prompt: PAE (Physical Address Extension) Support |
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>> Location: |
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>> (1) -> Processor type and features |
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>> Defined at arch/x86/Kconfig:1213 |
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>> Depends on: X86_32 [=n] && !HIGHMEM4G [=n] |
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>> Selected by: HIGHMEM64G [=n] && <choice> && !M486 [=n] |
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>> |
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>> |
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> Thanks. I did a little research into the whole PAE business, as |
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> obviously my knowledge of the matter in question was limited. |
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> |
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> If I understood it correctly, PAE is a method that allows 32-bit kernels |
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> access 4 or more Gb of RAM, which is normally the domain of 64-bit kernels. |
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> |
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> Seeing I've got 3 Gb of RAM, I arrived at the conclusion I don't need |
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> PAE enabled, do I? |
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> |
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> box0=; sed 1q /proc/meminfo |
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> MemTotal: 3107668 kB |
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That is correct, with 3G physica RAM, you will not benefit from using |
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PAE at all. I don't think it interferes with anything if you do have it, |
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I recall a time when RedHat shipped 32 bit kernels that were PAE-enabled. |
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Briefly, the way it works is that the kernel assigns blocks of memory to |
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different processes. So a single process can still only access 4G of |
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memory, but two different process don't anymore have to address the same |
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4G of memory like you must do without PAE. But you still don't get to |
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give your 32 bit database more than 4g of RAM |
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-- |
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Alan McKinnon |
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alan.mckinnon@×××××.com |