[Linuxppc-users] memmap kernel option on ubuntu 16.04 power8

[Brian Horton]

Greetings all.

I'm trying to run some tests with less memory than what's installed. the 
'mem=128G' option works, but it ends up putting all of the memory on the 
first numa node:

    available: 2 nodes (0,8)
    node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
    22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
      41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62
    63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79
    node 0 size: 130695 MB
    node 0 free: 10765 MB
    node 8 cpus: 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97
    98 99 100 101 102 103 104 105 106 107 108 109 110 111 112
    113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129
    130 131 132 133 134 135 136 137 138 139 140 141 142 143 1
    44 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159
    node 8 size: 0 MB
    node 8 free: 0 MB


I want 64G on each of the 2 numa nodes. Found this kernel option:

         memmap=nn[KMG]$ss[KMG]
                         [KNL,ACPI] Mark specific memory as reserved.
                         Region of memory to be reserved is from ss to 
ss+nn.
                         Example: Exclude memory from 0x18690000-0x1869ffff
                                  memmap=64K$0x18690000
                                  or
                                  memmap=0x10000$0x18690000

and it works on x86:

    available: 2 nodes (0-1)
    node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 24 25 26 27 28 29 30 31 32 33
    34 35
    node 0 size: 64315 MB
    node 0 free: 364 MB
    node 1 cpus: 12 13 14 15 16 17 18 19 20 21 22 23 36 37 38 39 40 41
    42 43 44 45 46 47
    node 1 size: 64507 MB
    node 1 free: 134 MB


but i can't get it to work on Ubuntu 16.04 Power8.

    /etc/default/grub:GRUB_CMDLINE_LINUX="'memmap=64G\$384G
    memmap=64G\$128G'"
    /boot/grub/grub.cfg:        linux       /vmlinux-4.10.0-33-generic
    root=/dev/mapper/p215n19--vg-root ro 'memmap=64G$384G
    memmap=64G$128G' splash quiet

    # cat /proc/cmdline
    root=/dev/mapper/p215n19--vg-root ro memmap=64G$384G memmap=64G$128G
    splash quiet


someone said that it worked on RHEL, so maybe it's an Ubuntu-specific bug..

thoughts? ideas?

thanks!  .bri.

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