Hi Wu,
Thanks, and will update the comments and msg in the next version. :)
2013/9/14 Jianguo Wu <wujianguo@xxxxxxxxxx>:
> Hi Tang,
>
> On 2013/9/13 17:30, 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 direct 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@xxxxxxxxxxxxxx>
>> Reviewed-by: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
>> ---
>> include/linux/memblock.h | 22 ++++++++++++++++++++++
>> mm/memblock.c | 13 +++++++++++++
>> 2 files changed, 35 insertions(+), 0 deletions(-)
>>
>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>> index 31e95ac..a7d3436 100644
>> --- a/include/linux/memblock.h
>> +++ b/include/linux/memblock.h
>> @@ -19,6 +19,11 @@
>>
>> #define INIT_MEMBLOCK_REGIONS 128
>>
>> +/* Allocation order. */
>
> s/order/direction/
>
>> +#define MEMBLOCK_DIRECTION_HIGH_TO_LOW 0
>> +#define MEMBLOCK_DIRECTION_LOW_TO_HIGH 1
>> +#define MEMBLOCK_DIRECTION_DEFAULT MEMBLOCK_DIRECTION_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_direction; /* allocate from higher or lower address */
>> phys_addr_t current_limit;
>> struct memblock_type memory;
>> struct memblock_type reserved;
>> @@ -148,6 +154,12 @@ phys_addr_t memblock_alloc_try_nid(phys_addr_t size, phys_addr_t align, int nid)
>>
>> phys_addr_t memblock_alloc(phys_addr_t size, phys_addr_t align);
>>
>> +static inline bool memblock_direction_bottom_up(void)
>> +{
>> + return memblock.current_direction == MEMBLOCK_DIRECTION_LOW_TO_HIGH;
>> +}
>> +
>> +
>> /* Flags for memblock_alloc_base() amd __memblock_alloc_base() */
>> #define MEMBLOCK_ALLOC_ANYWHERE (~(phys_addr_t)0)
>> #define MEMBLOCK_ALLOC_ACCESSIBLE 0
>> @@ -175,6 +187,16 @@ static inline void memblock_dump_all(void)
>> }
>>
>> /**
>> + * memblock_set_current_direction - Set current allocation direction to allow
>> + * allocating memory from higher to lower
>> + * address or from lower to higher address
>> + *
>> + * @direction: In which order to allocate memory. Could be
>
> s/order/direction/
>
>> + * MEMBLOCK_DIRECTION_{HIGH_TO_LOW|LOW_TO_HIGH}
>> + */
>> +void memblock_set_current_direction(int direction);
>> +
>> +/**
>> * memblock_set_current_limit - Set the current allocation limit to allow
>> * limiting allocations to what is currently
>> * accessible during boot
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index 0ac412a..f24ca2e 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_direction = MEMBLOCK_DIRECTION_DEFAULT,
>> .current_limit = MEMBLOCK_ALLOC_ANYWHERE,
>> };
>>
>> @@ -995,6 +996,18 @@ void __init_memblock memblock_trim_memory(phys_addr_t align)
>> }
>> }
>>
>> +void __init_memblock memblock_set_current_direction(int direction)
>> +{
>> + if (direction != MEMBLOCK_DIRECTION_HIGH_TO_LOW &&
>> + direction != MEMBLOCK_DIRECTION_LOW_TO_HIGH) {
>> + pr_warn("memblock: Failed to set allocation order. "
>> + "Invalid order type: %d\n", direction);
>
> s/order/direction/
>
>> + return;
>> + }
>> +
>> + memblock.current_direction = direction;
>> +}
>> +
>> void __init_memblock memblock_set_current_limit(phys_addr_t limit)
>> {
>> memblock.current_limit = limit;
>
>
>
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