Re: [PATCH 04/17] arm: get rid of superfluous __GFP_REPEAT

[Russell King - ARM Linux]

On Mon, May 30, 2016 at 11:14:46AM +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
> 
> __GFP_REPEAT has a rather weak semantic but since it has been introduced
> around 2.6.12 it has been ignored for low order allocations.
> 
> PGALLOC_GFP uses __GFP_REPEAT but none of the allocation which uses
> this flag is for more than order-2. This means that this flag has never
> been actually useful here because it has always been used only for
> PAGE_ALLOC_COSTLY requests.

I hear what you say, but...

commit 8c65da6dc89ccb605d73773b1dd617e72982d971
Author: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Date:   Sat Nov 30 12:52:31 2013 +0000

    ARM: pgd allocation: retry on failure

    Make pgd allocation retry on failure; we really need this to succeed
    otherwise fork() can trigger OOMs.

    Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>

and that's the change which introduced this, and it did solve a problem
for me.  So I'm not happy to give an ack for this change unless someone
can tell me why adding __GFP_REPEAT back then had a beneficial effect.
Maybe there was some other bug in the MM layer in 2013 which this change
happened to solve?

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