• Vitaly Kuznetsov's avatar
    memory_hotplug: introduce CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE · 8604d9e5
    Vitaly Kuznetsov authored
    This patchset continues the work I started with commit 31bc3858
    ("memory-hotplug: add automatic onlining policy for the newly added
    memory").
    
    Initially I was going to stop there and bring the policy setting logic
    to userspace.  I met two issues on this way:
    
     1) It is possible to have memory hotplugged at boot (e.g.  with QEMU).
        These blocks stay offlined if we turn the onlining policy on by
        userspace.
    
     2) My attempt to bring this policy setting to systemd failed, systemd
        maintainers suggest to change the default in kernel or ...  to use
        tmpfiles.d to alter the policy (which looks like a hack to me):
            https://github.com/systemd/systemd/pull/2938
    
    
    
    Here I suggest to add a config option to set the default value for the
    policy and a kernel command line parameter to make the override.
    
    This patch (of 2):
    
    Introduce config option to set the default value for memory hotplug
    onlining policy (/sys/devices/system/memory/auto_online_blocks).  The
    reason one would want to turn this option on are to have early onlining
    for hotpluggable memory available at boot and to not require any
    userspace actions to make memory hotplug work.
    
    [akpm@linux-foundation.org: tweak Kconfig text]
    Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
    Cc: Jonathan Corbet <corbet@lwn.net>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: David Vrabel <david.vrabel@citrix.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Igor Mammedov <imammedo@redhat.com>
    Cc: Lennart Poettering <lennart@poettering.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    8604d9e5