Re: [PATCH v1] mm: help the ALLOC_HARDER allocation pass the watermarki when CMA on

[Michal Hocko]

On Fri 23-03-18 15:57:32, Zhaoyang Huang wrote:
> For the type of 'ALLOC_HARDER' page allocation, there is an express
> highway for the whole process which lead the allocation reach __rmqueue_xxx
> easier than other type.
> However, when CMA is enabled, the free_page within zone_watermark_ok() will
> be deducted for number the pages in CMA type, which may cause the watermark
> check fail, but there are possible enough HighAtomic or Unmovable and
> Reclaimable pages in the zone. So add 'alloc_harder' here to
> count CMA pages in to clean the obstacles on the way to the final.

This is no longer the case in the current mmotm tree. Have a look at
Joonsoo's zone movable based CMA patchset http://lkml.kernel.org/r/1512114786-5085-1-git-send-email-iamjoonsoo.kim@xxxxxxx

> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxxxxxx>
> ---
>  mm/page_alloc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 635d7dd..cc18620 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3045,8 +3045,11 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
>  
>  
>  #ifdef CONFIG_CMA
> -	/* If allocation can't use CMA areas don't use free CMA pages */
> -	if (!(alloc_flags & ALLOC_CMA))
> +	/*
> +	 * If allocation can't use CMA areas and no alloc_harder set for none
> +	 * order0 allocation, don't use free CMA pages.
> +	 */
> +	if (!(alloc_flags & ALLOC_CMA) && (!alloc_harder || !order))
>  		free_pages -= zone_page_state(z, NR_FREE_CMA_PAGES);
>  #endif
>  
> -- 
> 1.9.1
> 

-- 
Michal Hocko
SUSE Labs