On May 26, 2015, at 11:52 AM, yalin wang wrote:
> 2015-05-25 0:02 GMT+08:00 Jungseok Lee <jungseoklee85@xxxxxxxxx>:
>> Fork-routine sometimes fails to get a physically contiguous region for
>> thread_info on 4KB page system although free memory is enough. That is,
>> a physically contiguous region, which is currently 16KB, is not available
>> since system memory is fragmented.
>>
>> This patch tries to solve the problem as allocating thread_info memory
>> from vmalloc space, not 1:1 mapping one. The downside is one additional
>> page allocation in case of vmalloc. However, vmalloc space is large enough,
>> around 240GB, under a combination of 39-bit VA and 4KB page. Thus, it is
>> not a big tradeoff for fork-routine service.
>>
>> Suggested-by: Sungjinn Chung <barami97@xxxxxxxxx>
>> Signed-off-by: Jungseok Lee <jungseoklee85@xxxxxxxxx>
>> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
>> Cc: Will Deacon <will.deacon@xxxxxxx>
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Cc: linux-mm@xxxxxxxxx
>> ---
>> arch/arm64/Kconfig | 12 ++++++++++++
>> arch/arm64/include/asm/thread_info.h | 9 +++++++++
>> arch/arm64/kernel/process.c | 7 +++++++
>> 3 files changed, 28 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 99930cf..93c236a 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -536,6 +536,18 @@ config ARCH_SELECT_MEMORY_MODEL
>> config HAVE_ARCH_PFN_VALID
>> def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
>>
>> +config ARCH_THREAD_INFO_ALLOCATOR
>> + bool "Enable vmalloc based thread_info allocator (EXPERIMENTAL)"
>> + depends on ARM64_4K_PAGES
>> + default n
>> + help
>> + This feature enables vmalloc based thread_info allocator. It
>> + prevents fork-routine from begin failed to obtain physically
>> + contiguour region due to memory fragmentation on low system
>> + memory platforms.
>> +
>> + If unsure, say N
>> +
>> config HW_PERF_EVENTS
>> bool "Enable hardware performance counter support for perf events"
>> depends on PERF_EVENTS
>> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
>> index dcd06d1..e753e59 100644
>> --- a/arch/arm64/include/asm/thread_info.h
>> +++ b/arch/arm64/include/asm/thread_info.h
>> @@ -61,6 +61,15 @@ struct thread_info {
>> #define init_thread_info (init_thread_union.thread_info)
>> #define init_stack (init_thread_union.stack)
>>
>> +#ifdef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
>> +#define alloc_thread_info_node(tsk, node) \
>> +({ \
>> + __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE, VMALLOC_START, \
>> + VMALLOC_END, GFP_KERNEL, PAGE_KERNEL, 0, \
>> + NUMA_NO_NODE, __builtin_return_address(0)); \
>> +})
> why not add __GFP_HIGHMEM, if you decided to use vmalloc() alloc stack pages?
I do not add the flag since there is no high memory on a current ARM64 kernel.
It would be helpful to review include/linux/gfp.h and the following code snippet
from arch/arm64/kernel/module.c.
void *module_alloc(unsigned long size)
{
return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
NUMA_NO_NODE, __builtin_return_address(0));
}
Best Regards
Jungseok Lee
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