Re: [RFC PATCH] mm: check global free_list if there is ongoing reclaiming when pcp fail

[Zhaoyang Huang]

On Mon, Sep 19, 2022 at 6:22 PM Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, Sep 16, 2022 at 06:58:12PM +0800, zhaoyang.huang wrote:
> > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> >
> > Check the global free list again even if rmqueue_bulk failed for pcp pages when
> > there is ongoing reclaiming, which could eliminate potential direct reclaim by
> > chance.
> >
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> Patch does not apply and may be based on a custom kernel that introduced
> a problem. There is no description of what problem this is trying to
> fix. Checking the status of reclaim for a specific zone in this path would
> be a little unexpected.  If allocation pressure is exceeding the ability
> of reclaim to make progress then the caller likely needs to take action
> like direct reclaim. If the allocation failure is due to a high-order
> failure then it may need to enter direct compaction etc.
Agree with the above comment. This is a proposal aiming at avoiding
direct reclaiming things with minimum cost, that is to say, about 5
CPU instructions in return with the overhead of function calls which
has both of several loops inside and potential throttle sleep by IO
congestion etc.
>
> --
> Mel Gorman
> SUSE Labs