Red Hat Bugzilla – Bug 212986
System with 4gb memory has only 3gb allocated.
Last modified: 2007-11-30 17:11:47 EST
Description of problem: 4gb memory in system only displays as ~3 GB. Rebooted and tried memtest which shows all 4gb memory. Previous FC5 showed all 4gb. Version-Release number of selected component (if applicable): uname -rvpsm Linux 2.6.18-1.2798.fc6 #1 SMP Mon Oct 16 14:37:32 EDT 2006 i686 athlon (Opteron 170) How reproducible: Always Steps to Reproduce: 1. Boot current release i686 kerenel ( non PAE ) 2. 3. Actual results: dmesg | grep mem Memory: 3103988k/4194304k available (2138k kernel code, 40368k reserved, 868k data, 240k init, 2228160k highmem) Freeing initrd memory: 2242k freed highmem bounce pool size: 64 pages Total HugeTLB memory allocated, 0 Non-volatile memory driver v1.2 Freeing unused kernel memory: 240k freed ohci_hcd 0000:00:02.0: irq 225, io mem 0xd5003000 ehci_hcd 0000:00:02.1: irq 233, io mem 0xfeb00000 /dev/vmnet: hub 0 does not exist, allocating memory. Expected results: Ability to use 4gb. Additional info:
It says : "4194304k". The kernel does see the 4GB. IF you can attach the full dmesg, it will point otu to where the 1GB is going.
After looking at the full dmesg, I noticed towards the top it says to use a PAE kernel even though I have 4GB installed ( 4 x 1024 Corsair Cas2 DDR400 ). So I've changed to the PAE kernel which has resolved the issue. If you would like me to reboot to a non PAE kernel and paste the output, I am quite happy to do so, however this is the PAE output. Notice the 4224MB HIMEM. I'm not sure how it comes to this figure as 4 x 1024 = 4096mb. Linux version 2.6.18-1.2798.fc6PAE (brewbuilder@hs20-bc2-4.build.redhat.com) (gcc version 4.1.1 20061011 (Red Hat 4.1.1-30)) #1 SMP Mon Oct 16 14:54:22 EDT 2006 BIOS-provided physical RAM map: BIOS-e820: 0000000000000000 - 000000000009e800 (usable) BIOS-e820: 000000000009e800 - 00000000000a0000 (reserved) BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 00000000bfff0000 (usable) BIOS-e820: 00000000bfff0000 - 00000000bfff3000 (ACPI NVS) BIOS-e820: 00000000bfff3000 - 00000000c0000000 (ACPI data) BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved) BIOS-e820: 00000000fec00000 - 0000000100000000 (reserved) BIOS-e820: 0000000100000000 - 0000000140000000 (usable) 4224MB HIGHMEM available. 896MB LOWMEM available. found SMP MP-table at 000f59c0 NX (Execute Disable) protection: active On node 0 totalpages: 1310720 DMA zone: 4096 pages, LIFO batch:0 Normal zone: 225280 pages, LIFO batch:31 HighMem zone: 1081344 pages, LIFO batch:31 The non PAE kernel only allocated 3200MB of HIMEM on my system. Would it because it thinks I have > 4gb with the 4224mb. ?
The reason why the non-PAE kernel allocated the 3.2GB is b/c it cannot use the other memory. This is due to how much the kernel can map each page (4KB) in the memory. I am closing the bug as NOTABUG. Thanks for finding the solution.