Re: [PATCH 05/11] memblock: Introduce allocation order to memblock.

[Wanpeng Li <liwanp@linux.vnet.ibm.com>]

Hi Tang,
On Tue, Aug 27, 2013 at 05:37:42PM +0800, Tang Chen wrote:
>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 from high address to low.
>So this patch introduces the allocation order to memblock. It could be
>used to tell memblock to allocate memory from high to low or from low
>to high.
>
>Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
>Reviewed-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>---
> include/linux/memblock.h |   15 +++++++++++++++
> mm/memblock.c            |   13 +++++++++++++
> 2 files changed, 28 insertions(+), 0 deletions(-)
>
>diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>index cabd685..f233c1f 100644
>--- a/include/linux/memblock.h
>+++ b/include/linux/memblock.h
>@@ -19,6 +19,11 @@
>
> #define INIT_MEMBLOCK_REGIONS	128
>
>+/* Allocation order. */

How about replace "Allocation order" by "Allocation sequence". 

The "Allocation order" is ambiguity.

Regards,
Wanpeng Li 

>+#define MEMBLOCK_ORDER_HIGH_TO_LOW	0
>+#define MEMBLOCK_ORDER_LOW_TO_HIGH	1
>+#define MEMBLOCK_ORDER_DEFAULT		MEMBLOCK_ORDER_HIGH_TO_LOW
>+
> struct memblock_region {
> 	phys_addr_t base;
> 	phys_addr_t size;
>@@ -35,6 +40,7 @@ struct memblock_type {
> };
>
> struct memblock {
>+	int current_order;	/* allocate from higher or lower address */
> 	phys_addr_t current_limit_low;	/* lower boundary of accessable range */
> 	phys_addr_t current_limit_high;	/* upper boundary of accessable range */
> 	struct memblock_type memory;
>@@ -174,6 +180,15 @@ static inline void memblock_dump_all(void)
> }
>
> /**
>+ * memblock_set_current_order - Set the current allocation order to allow
>+ *                         allocating memory from higher to lower address or
>+ *                         from lower to higher address
>+ * @order: In which order to allocate memory. Could be
>+ *         MEMBLOCK_ORDER_{HIGH_TO_LOW|LOW_TO_HIGH}
>+ */
>+void memblock_set_current_order(int order);
>+
>+/**
>  * memblock_set_current_limit_low - Set the current allocation lower limit to
>  *                         allow limiting allocations to what is currently
>  *                         accessible during boot
>diff --git a/mm/memblock.c b/mm/memblock.c
>index 54c1c2e..8f1e2d4 100644
>--- a/mm/memblock.c
>+++ b/mm/memblock.c
>@@ -32,6 +32,7 @@ struct memblock memblock __initdata_memblock = {
> 	.reserved.cnt		= 1,	/* empty dummy entry */
> 	.reserved.max		= INIT_MEMBLOCK_REGIONS,
>
>+	.current_order		= MEMBLOCK_ORDER_DEFAULT,
> 	.current_limit_low	= 0,
> 	.current_limit_high	= MEMBLOCK_ALLOC_ANYWHERE,
> };
>@@ -989,6 +990,18 @@ void __init_memblock memblock_trim_memory(phys_addr_t align)
> 	}
> }
>
>+void __init_memblock memblock_set_current_order(int order)
>+{
>+	if (order != MEMBLOCK_ORDER_HIGH_TO_LOW &&
>+	    order != MEMBLOCK_ORDER_LOW_TO_HIGH) {
>+		pr_warn("memblock: Failed to set allocation order. "
>+			"Invalid order type: %d\n", order);
>+		return;
>+	}
>+
>+	memblock.current_order = order;
>+}
>+
> void __init_memblock memblock_set_current_limit_low(phys_addr_t limit)
> {
> 	memblock.current_limit_low = limit;
>-- 
>1.7.1
>
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