Re: CMA and zone watermarks

Minchan Kim
2012-10-09T03:06:12Z

Hello,

On Mon, Oct 08, 2012 at 05:41:14PM +0200, Rabin Vincent wrote:
> It appears that when CMA is enabled, the zone watermarks are not properly
> respected, leading to for example GFP_NOWAIT allocations getting access to the
> high pools.
>
> I ran the following test code which simply allocates pages with GFP_NOWAIT
> until it fails, and then tries GFP_ATOMIC. Without CMA, the GFP_ATOMIC
> allocation succeeds, with CMA, it fails too.

Good spot. By wrong zone_watermark_check, it can consume reserved memory pool.

>
> Logs attached (includes my patch which prints the migration type in the failure
> message http://marc.info/?l=linux-mm&m=134971041701306&w=2), taken on 3.6
> kernel.
>

Fortunately, recently, Bart sent a patch about that.
http://marc.info/?l=linux-mm&m=134763299016693&w=2

Could you test above patches in your kernel?
You have to apply [2/4], [3/4], [4/4] and don't need [1/4].

Thanks.

--
Kind regards,
Minchan Kim