Re: [PATCH] fix page_alloc for larger I/O segments (improved)

[Mark Lord <liml@rtr.ca>]

Andrew Morton wrote:
> On Thu, 13 Dec 2007 19:57:29 -0500
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
>> On Thu, 2007-12-13 at 19:46 -0500, Mark Lord wrote:
>>> "Improved version", more similar to the 2.6.23 code:
>>>
>>> Fix page allocator to give better chance of larger contiguous segments (again).
>>>
>>> Signed-off-by: Mark Lord <mlord@pobox.com
>>> ---
>>>
>>> --- old/mm/page_alloc.c	2007-12-13 19:25:15.000000000 -0500
>>> +++ linux-2.6/mm/page_alloc.c	2007-12-13 19:43:07.000000000 -0500
>>> @@ -760,7 +760,7 @@
>>>  		struct page *page = __rmqueue(zone, order, migratetype);
>>>  		if (unlikely(page == NULL))
>>>  			break;
>>> -		list_add(&page->lru, list);
>>> +		list_add_tail(&page->lru, list);
>> Could we put a big comment above this explaining to the would be vm
>> tweakers why this has to be a list_add_tail, so we don't end up back in
>> this position after another two years?
>>
> 
> Already done ;)
..

I thought of the comment as I rushed off for dinner.
Thanks, Andrew!

> --- a/mm/page_alloc.c~fix-page_alloc-for-larger-i-o-segments-fix
> +++ a/mm/page_alloc.c
> @@ -847,6 +847,10 @@ static int rmqueue_bulk(struct zone *zon
>  		struct page *page = __rmqueue(zone, order, migratetype);
>  		if (unlikely(page == NULL))
>  			break;
> +		/*
> +		 * Doing a list_add_tail() here helps us to hand out pages in
> +		 * ascending physical-address order.
> +		 */
>  		list_add_tail(&page->lru, list);
>  		set_page_private(page, migratetype);
>  	}
> _