------- Comment From geral...@de.ibm.com 2016-08-30 13:25 EDT-------
This actually "works as designed", and the missing block is not only block 10
but also block 14. Both blocks contain part of the standby memory, but not
aligned to the Linux memory block size. Block 10 also contains the crashkernel
memory, if you try it w/o crashkernel memory (or use a more current kernel, as
this behaviour was changed) then it should be visible but cannot be set offline.
The reason why you can only use 768 MB of your 1 GB standby memory is
because both the start and end address (in block 10 and 14) are not
aligned to the Linux memory block size of 256 MB, which leaves only 768
MB of usable standby memory (i.e. standby memory that consumes a whole
Linux memory block).
The following commit introduced this "capping" and also a message that
you should find in your dmesg output, unfortunately w/o the kmsg
description because Ubuntu has no kmsg man pages:
commit 8741ce6d114873e482b1ef298d6537d18ff393d3
Author: Michael Holzheu <holz...@linux.vnet.ibm.com>
Date: Wed Apr 1 18:49:11 2015 +0200
s390/mm: Fix memory hotplug for unaligned standby memory
Commit 27356f54c8c3 ("mm/hotplug: verify hotplug memory range")
introduced a check that makes add_memory() only accept section size
aligned memory.
Therefore on z/VM systems, where standby memory is not aligned, no
standby memory is registered at all.
Example:
#cp def store 3504M standby 2336M
00: CP Q V STORE
00: STORAGE = 3504M MAX = 6G INC = 8M STANDBY = 2336M RESERVED = 0
For this setup the following error message is printed:
Section-unaligned hotplug range: start 0xdb000000, size 0x92000000
So fix this and register aligned memory in "sclp_cmd.c". This means
that for the corner cases where the standby memory is not aligned we
loose some memory.
In order to inform the user about the potential loss of standby memory,
we add a new message for each added standby block and print how
much of the standby memory is usable, for example:
sclp_cmd.4336b4: Standby memory at 0x50000000 (256M of 256M usable)
sclp_cmd.4336b4: Standby memory at 0xb0000000 (256M of 256M usable)
sclp_cmd.4336b4: Standby memory at 0xdb000000 (2048M of 2336M usable)
We also ensure that a potential memory block that contains both "assigned"
and "standby" memory cannot be setup offline.
Reviewed-by: Gerald Schaefer <gerald.schae...@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carst...@de.ibm.com>
Signed-off-by: Michael Holzheu <holz...@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com>
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You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1618203
Title:
missing memory slot at /sys/bus/memory/devices when starting memory
size is not a multiple of block size
Status in Ubuntu on IBM z Systems:
New
Status in linux package in Ubuntu:
New
Bug description:
== Comment: #0 - Ofer Baruch - 2016-08-28 07:41:53 ==
When you set the memory size of a Ubuntu Guest to a number which is not a
multiple of the memory block size (in our case 256MB) there are missing memory
slots at /sys/bus/memory/devices.
for example setting memory like this:
STORAGE = 2704M MAX = 15000M INC = 8M STANDBY = 512M RESERVED = 512M
will cause memory slot 10 to be missing:
root@UBU9LT1:/sys/bus/memory/devices# ll
total 0
drwxr-xr-x 2 root root 0 Aug 24 09:43 ./
drwxr-xr-x 4 root root 0 Aug 24 09:43 ../
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory0 ->
../../../devices/system/memory/memory0/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory1 ->
../../../devices/system/memory/memory1/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory11 ->
../../../devices/system/memory/memory11/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory12 ->
../../../devices/system/memory/memory12/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory13 ->
../../../devices/system/memory/memory13/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory2 ->
../../../devices/system/memory/memory2/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory3 ->
../../../devices/system/memory/memory3/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory4 ->
../../../devices/system/memory/memory4/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory5 ->
../../../devices/system/memory/memory5/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory6 ->
../../../devices/system/memory/memory6/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory7 ->
../../../devices/system/memory/memory7/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory8 ->
../../../devices/system/memory/memory8/
lrwxrwxrwx 1 root root 0 Aug 24 09:43 memory9 ->
../../../devices/system/memory/memory9/
lsmem shows:
root@UBU9LT1:/sys/bus/memory/devices# lsmem -a
Address Range Size (MB) State Removable Device
===============================================================================
0x0000000000000000-0x000000000fffffff 256 online no 0-31
0x0000000010000000-0x000000001fffffff 256 online yes 32-63
0x0000000020000000-0x000000002fffffff 256 online yes 64-95
0x0000000030000000-0x000000003fffffff 256 online yes 96-127
0x0000000040000000-0x000000004fffffff 256 online yes 128-159
0x0000000050000000-0x000000005fffffff 256 online yes 160-191
0x0000000060000000-0x000000006fffffff 256 online yes 192-223
0x0000000070000000-0x000000007fffffff 256 online no 224-255
0x0000000080000000-0x000000008fffffff 256 online yes 256-287
0x0000000090000000-0x000000009fffffff 256 online no 288-319
0x00000000b0000000-0x00000000bfffffff 256 offline - 352-383
0x00000000c0000000-0x00000000cfffffff 256 offline - 384-415
0x00000000d0000000-0x00000000dfffffff 256 offline - 416-447
although there is 1GB of memory in standby and reserved i can only
vary online 768MB as there are only 3 offline blocks... there should
be 4 blocks available... specifically block number 10 is missing
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