Re: [PATCH part1 v6 2/6] memblock: Introduce bottom-up allocation mode

[Toshi Kani <toshi.kani@hp.com>]

On Fri, 2013-10-04 at 09:58 +0800, Zhang Yanfei wrote:
> From: Tang Chen <tangchen@cn.fujitsu.com>
> 
> 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: Tang Chen <tangchen@cn.fujitsu.com>
> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>

Thanks for the update.

Acked-by: Toshi Kani <toshi.kani@hp.com>

-Toshi



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