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Hello |
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I would like to share my experience with ram issue on gentoo (1.12.13) |
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I am running 64bit xen fedora kernel 2.6.31-6 |
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(http://wiki.xensource.com/xenwiki/XenParavirtOps) |
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Why? - because previous 2.6.31-r7 from |
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http://code.google.com/p/gentoo-xen-kernel/downloads/list was unstable and |
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also only 3GB ram were visible. |
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|
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There are 4GB ram installed on server. With standard kernel (2.6.30-r5), I |
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am able to see it all. Because of this, I disqualify grub bug. |
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With xen kernel, I saw only 3GB. |
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|
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xm dmesg: |
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(XEN) Xen-e820 RAM map: |
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(XEN) 0000000000000000 - 000000000009f000 (usable) |
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(XEN) 000000000009f000 - 00000000000a0000 (reserved) |
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(XEN) 00000000000f0000 - 0000000000100000 (reserved) |
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(XEN) 0000000000100000 - 00000000bbeb0000 (usable) <----------- |
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3GB |
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(XEN) 00000000bbeb0000 - 00000000bbee3000 (ACPI NVS) |
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(XEN) 00000000bbee3000 - 00000000bbef0000 (ACPI data) |
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(XEN) 00000000bbef0000 - 00000000bbf00000 (reserved) |
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(XEN) 00000000bc000000 - 00000000c0000000 (reserved) |
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(XEN) 00000000f0000000 - 00000000f4000000 (reserved) |
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(XEN) 00000000fec00000 - 0000000100000000 (reserved) |
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(XEN) 0000000100000000 - 0000000140000000 (usable) <--------- 1 |
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GB |
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(XEN) System RAM: 4030MB (4127036kB) |
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|
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I do not know how this is possible: 140000000 = 5120MB and only 4030MB are |
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installed. |
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|
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In standard dmesg output (just "dmesg" in dom0, not "xm dmesg") I saw only |
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3GB address space. |
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I double checked kernel configuration and compared with standard kernel |
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config, however no dirrefence found (except xen options). |
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|
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|
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lnx2 linux-2.6.31-6-xen # grep -i mem .config | grep -v "#" |
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CONFIG_SHMEM=y |
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CONFIG_XEN_MAX_DOMAIN_MEMORY=32 |
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CONFIG_ARCH_SPARSEMEM_DEFAULT=y |
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CONFIG_ARCH_SPARSEMEM_ENABLE=y |
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CONFIG_ARCH_SELECT_MEMORY_MODEL=y |
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CONFIG_SELECT_MEMORY_MODEL=y |
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CONFIG_SPARSEMEM_MANUAL=y |
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CONFIG_SPARSEMEM=y |
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CONFIG_HAVE_MEMORY_PRESENT=y |
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CONFIG_SPARSEMEM_EXTREME=y |
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CONFIG_SPARSEMEM_VMEMMAP_ENABLE=y |
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CONFIG_SPARSEMEM_VMEMMAP=y |
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CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK=y |
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CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y |
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CONFIG_INPUT_FF_MEMLESS=y |
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CONFIG_DEVKMEM=y |
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CONFIG_FIX_EARLYCON_MEM=y |
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CONFIG_FIRMWARE_MEMMAP=y |
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CONFIG_DEBUG_MEMORY_INIT=y |
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CONFIG_HAVE_ARCH_KMEMCHECK=y |
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CONFIG_ASYNC_MEMCPY=y |
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CONFIG_HAS_IOMEM=y |
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|
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|
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lnx2 linux-2.6.31-6-xen # grep -i ram .config | grep -v "#" |
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CONFIG_X86_TRAMPOLINE=y |
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CONFIG_SCHED_OMIT_FRAME_POINTER=y |
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CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK=y |
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CONFIG_BLK_DEV_RAM=y |
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CONFIG_BLK_DEV_RAM_COUNT=16 |
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CONFIG_BLK_DEV_RAM_SIZE=16384 |
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CONFIG_NVRAM=y |
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CONFIG_FRAMEBUFFER_CONSOLE=y |
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CONFIG_FRAME_WARN=2048 |
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CONFIG_ARCH_WANT_FRAME_POINTERS=y |
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CONFIG_FRAME_POINTER=y |
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lnx2 linux-2.6.31-6-xen # |
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|
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|
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Another symptom: |
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|
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xm top: |
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======= |
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dom0 = 4GB |
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|
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xm list: |
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======== |
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dom0= 3GB |
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|
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Once VPS was started, dom0 ram size was decreased. So only 3GB were |
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available for dom0 + VPS |
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|
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|
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|
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As a workaround I added dom0_mem=512M to kernel line in grub.conf |
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|
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title XEN-6-fedora |
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root (hd0,0) |
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kernel /boot/xen.gz dom0_mem=512M |
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module /boot/vmlinuz-2.6.31-6-xen-dom0 root=/dev/md0 |
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acpi_enforce_resources=lax |
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|
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|
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xm top: |
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======= |
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dom0 = 512MB |
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|
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xm list: |
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======== |
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dom0= 512MB |
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|
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Now, I can see only 512MB in dom0, however rest of memory (3,5GB) is |
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usable for VPS :) :) :) |
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|
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I was searching on google over 2 months, but noone report this issue (some |
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users had turned off PAE on 32bit, some had wrongly configured BIOS). |
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So I hope that this mail will help to someone who have the same problem, |
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or that someone will find reason of this strangeness. |
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|
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|
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Thanks and regards |
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|
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samox86 |
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lnx@×××.sk |
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