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

From: Zhang Yanfei
Date: Sun Jun 16 2013 - 21:56:05 EST

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

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.

Zhang Yanfei
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