Re: [PATCH 3/3] vm: writeout watermarks

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

Nikita has a customer using large percentage of RAM for 
a kernel module, which results in get_dirty_limits() misbehaviour
since

        unsigned long available_memory = total_pages;

It should work on the amount of cacheable pages instead.

He's got a patch but I dont remember the URL. Nikita?

On Tue, Nov 01, 2005 at 04:21:15PM +1100, Nick Piggin wrote:
> 3/3
> 
> -- 
> SUSE Labs, Novell Inc.
> 

> Slightly change the writeout watermark calculations so we keep background
> and synchronous writeout watermarks in the same ratios after adjusting them.
> This ensures we should always attempt to start background writeout before
> synchronous writeout.
> 
> Signed-off-by: Nick Piggin <npiggin@suse.de>
> 
> 
> Index: linux-2.6/mm/page-writeback.c
> ===================================================================
> --- linux-2.6.orig/mm/page-writeback.c	2005-11-01 13:41:39.000000000 +1100
> +++ linux-2.6/mm/page-writeback.c	2005-11-01 14:29:27.000000000 +1100
> @@ -165,9 +165,11 @@ get_dirty_limits(struct writeback_state 
>  	if (dirty_ratio < 5)
>  		dirty_ratio = 5;
>  
> -	background_ratio = dirty_background_ratio;
> -	if (background_ratio >= dirty_ratio)
> -		background_ratio = dirty_ratio / 2;
> +	/*
> +	 * Keep the ratio between dirty_ratio and background_ratio roughly
> +	 * what the sysctls are after dirty_ratio has been scaled (above).
> +	 */
> +	background_ratio = dirty_background_ratio * dirty_ratio/vm_dirty_ratio;
>  
>  	background = (background_ratio * available_memory) / 100;
>  	dirty = (dirty_ratio * available_memory) / 100;