Subject: [PATCH] fixup: mm: alloc_contig_range: increase min_free_kbytes during allocation

From: [email-masked] (Maxime Coquelin)
Date: Wed, 12 Oct 2011 15:01:47 +0200

Hello Marek,

On 10/12/2011 01:08 PM, Marek Szyprowski wrote:
> Signed-off-by: Marek Szyprowski<[email-masked]>
> ---
>   mm/page_alloc.c |   15 ++++++++++++---
>   1 files changed, 12 insertions(+), 3 deletions(-)
>
> Hello Maxime,
>
> Please check if this patch fixes your lockup issue. It is a bit cruel,
> but it looks that in case of real low-memory situation page allocation
> is very complex task which usually ends in waiting for the io/fs and
> free pages that really don't arrive at all.
Thanks for the reactivity.
We just tested it, we no more faced the lockup. Instead, the OOM Killer 
is triggered and contiguous allocation succeed.
I'm not familiar enough with page_alloc.c to detect any side effects 
this patch could bring.

> Best regards
> --
> Marek Szyprowski
> Samsung Poland R&D Center
>
>
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 055aa4c..45473e9 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5872,6 +5872,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>   		       gfp_t flags, unsigned migratetype)
>   {
>   	unsigned long outer_start, outer_end;
> +	unsigned int count = end - start;
>   	int ret;
>
>   	/*
> @@ -5900,7 +5901,10 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>   	ret = __start_isolate_page_range(pfn_to_maxpage(start),
>   					 pfn_to_maxpage_up(end), migratetype);
>   	if (ret)
> -		goto done;
> +		return ret;
> +
> +	min_free_kbytes += count * PAGE_SIZE / 1024;
> +	setup_per_zone_wmarks();
>
>   	ret = __alloc_contig_migrate_range(start, end);
>   	if (ret)
> @@ -5922,8 +5926,10 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>
>   	ret = 0;
>   	while (!PageBuddy(pfn_to_page(start&  (~0UL<<  ret))))
> -		if (WARN_ON(++ret>= MAX_ORDER))
> -			return -EINVAL;
> +		if (WARN_ON(++ret>= MAX_ORDER)) {
> +			ret = -EINVAL;
> +			goto done;
> +		}
>
>   	outer_start = start&  (~0UL<<  ret);
>   	outer_end   = alloc_contig_freed_pages(outer_start, end, flags);
> @@ -5936,6 +5942,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>
>   	ret = 0;
>   done:
> +	min_free_kbytes -= count * PAGE_SIZE / 1024;
> +	setup_per_zone_wmarks();
> +
>   	__undo_isolate_page_range(pfn_to_maxpage(start), pfn_to_maxpage_up(end),
>   				  migratetype);
>   	return ret;

Best regards,
Maxime