Re: [PATCH] mm/thp: fix comments in transparent_hugepage_flags

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

On Thu, Sep 05, 2013 at 11:04:22AM +0800, Jianguo Wu wrote:
>Hi Wanpeng,
>
>On 2013/9/5 10:11, Wanpeng Li wrote:
>
>> Hi Jianguo,
>> On Wed, Sep 04, 2013 at 09:30:22PM +0800, Jianguo Wu wrote:
>>> Since commit d39d33c332(thp: enable direct defrag), defrag is enable
>>> for all transparent hugepage page faults by default, not only in
>>> MADV_HUGEPAGE regions.
>>>
>>> Signed-off-by: Jianguo Wu <wujianguo@huawei.com>
>>> ---
>>> mm/huge_memory.c | 6 ++----
>>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index a92012a..abf047e 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -28,10 +28,8 @@
>>>
>>> /*
>>>  * By default transparent hugepage support is enabled for all mappings
>> 
>> This is also stale. TRANSPARENT_HUGEPAGE_ALWAYS is not configured by default in
>> order that avoid to risk increase the memory footprint of applications w/o a 
>> guaranteed benefit.
>> 
>
>Right, how about this:
>
>By default transparent hugepage support is disabled in order that avoid to risk

I don't think it's disabled. TRANSPARENT_HUGEPAGE_MADVISE is configured
by default.

Regards,
Wanpeng Li 

>increase the memory footprint of applications w/o a guaranteed benefit, and
>khugepaged scans all mappings when transparent hugepage enabled.
>Defrag is invoked by khugepaged hugepage allocations and by page faults for all
>hugepage allocations.
>
>Thanks,
>Jianguo Wu
>
>> Regards,
>> Wanpeng Li 
>> 
>>> - * and khugepaged scans all mappings. Defrag is only invoked by
>>> - * khugepaged hugepage allocations and by page faults inside
>>> - * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
>>> - * allocations.
>>> + * and khugepaged scans all mappings. Defrag is invoked by khugepaged
>>> + * hugepage allocations and by page faults for all hugepage allocations.
>>>  */
>>> unsigned long transparent_hugepage_flags __read_mostly =
>>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
>>> -- 
>>> 1.8.1.2
>>>
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>
>

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