• Tang Chen's avatar
    mm/memblock.c: introduce bottom-up allocation mode · 79442ed1
    Tang Chen authored
    
    
    The Linux kernel cannot migrate pages used by the kernel.  As a result,
    kernel pages cannot be hot-removed.  So we cannot allocate hotpluggable
    memory for the kernel.
    
    ACPI SRAT (System Resource Affinity Table) contains the memory hotplug
    info.  But before SRAT is parsed, memblock has already started to allocate
    memory for the kernel.  So we need to prevent memblock from doing this.
    
    In a memory hotplug system, any numa node the kernel resides in should be
    unhotpluggable.  And for a modern server, each node could have at least
    16GB memory.  So memory around the kernel image is highly likely
    unhotpluggable.
    
    So the basic idea is: Allocate memory from the end of the kernel image and
    to the higher memory.  Since memory allocation before SRAT is parsed won't
    be too much, it could highly likely be in the same node with kernel image.
    
    The current memblock can only allocate memory top-down.  So this patch
    introduces a new bottom-up allocation mode to allocate memory bottom-up.
    And later when we use this allocation direction to allocate memory, we
    will limit the start address above the kernel.
    
    Signed-off-by: default avatarTang Chen <tangchen@cn.fujitsu.com>
    Signed-off-by: default avatarZhang Yanfei <zhangyanfei@cn.fujitsu.com>
    Acked-by: default avatarToshi Kani <toshi.kani@hp.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
    Cc: Thomas Renninger <trenn@suse.de>
    Cc: Yinghai Lu <yinghai@kernel.org>
    Cc: Jiang Liu <jiang.liu@huawei.com>
    Cc: Wen Congyang <wency@cn.fujitsu.com>
    Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
    Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
    Cc: Mel Gorman <mgorman@suse.de>
    Cc: Michal Nazarewicz <mina86@mina86.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    79442ed1