Re: [PATCH] mm: Add unlikely for current_order test

[Zhang Yanfei]

Hi David,

On 06/17/2013 02:04 AM, David Rientjes wrote:
> On Sat, 15 Jun 2013, Zhang Yanfei wrote:
> 
>> From: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
>>
>> Since we have an unlikely for the "current_order >= pageblock_order / 2"
>> test above, adding an unlikely for this "current_order >= pageblock_order"
>> test seems more appropriate.
>>
> 
> I don't understand the justification at all, current_order being unlikely 
> greater than or equal to pageblock_order / 2 doesn't imply at all that 
> it's unlikely that current_order is greater than or equal to 
> pageblock_order.
> 

hmmm... I am confused. Since current_order is >= pageblock_order / 2 is unlikely,
why current_order is >= pageblock_order isn't unlikely. Or there are other
tips?

Actually, I am also a little confused about why current_order should be
unlikely greater than or equal to pageblock_order / 2. When borrowing pages
with other migrate_type, we always search from MAX_ORDER-1, which is greater
or equal to pageblock_order.

-- 
Thanks.
Zhang Yanfei
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