------- Comment From [email protected] 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 <[email protected]> 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 <[email protected]> Reviewed-by: Heiko Carstens <[email protected]> Signed-off-by: Michael Holzheu <[email protected]> Signed-off-by: Martin Schwidefsky <[email protected]> -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1618203/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
