Re: [PATCH 02/12] mm: supporting variables and functions for balanced zone aging

Wu Fengguang <wfg <at> mail.ustc.edu.cn> wrote:
>
>  The zone aging rates are currently imbalanced,

ZONE_DMA is out of whack.  It shouldn't be, and I'm not aware of anyone
getting in and working out why.  I certainly wouldn't want to go and add
all this stuff without having a good understanding of _why_ it's out of
whack.  Perhaps it's just some silly bug, like the thing I pointed at in
the previous email.

> the gap can be as large as 3 times,

What's the testcase?

> which can severely damage read-ahead requests and shorten their
>  effective life time.

Have you any performance numbers for this?