Re: [RFC][PATCH 4/9] soft limit queue and priority

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-03 17:12:48]:

> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> Softlimitq. for memcg.
> 
> Implements an array of queue to list memcgs, array index is determined by
> the amount of memory usage excess the soft limit.
> 
> While Balbir's one uses RB-tree and my old one used a per-zone queue
> (with round-robin), this is one of mixture of them.
> (I'd like to use rotation of queue in later patches)
> 
> Priority is determined by following.
>    Assume unit = total pages/1024. (the code uses different value)
>    if excess is...
>       < unit,          priority = 0, 
>       < unit*2,        priority = 1,
>       < unit*2*2,      priority = 2,
>       ...
>       < unit*2^9,      priority = 9,
>       < unit*2^10,     priority = 10, (> 50% to total mem)
> 
> This patch just includes queue management part and not includes 
> selection logic from queue. Some trick will be used for selecting victims at
> soft limit in efficient way.
> 
> And this equips 2 queues, for anon and file. Inset/Delete of both list is
> done at once but scan will be independent. (These 2 queues are used later.)
> 
> Major difference from Balbir's one other than RB-tree is bahavior under
> hierarchy. This one adds all children to queue by checking hierarchical
> priority. This is for helping per-zone usage check on victim-selection logic.
> 
> Changelog: v1->v2
>  - fixed comments.
>  - change base size to exponent.
>  - some micro optimization to reduce code size.
>  - considering memory hotplug, it's not good to record a value calculated
>    from totalram_pages at boot and using it later is bad manner. Fixed it.
>  - removed soft_limit_lock (spinlock) 
>  - added soft_limit_update counter for avoiding mulptiple update at once.
>    
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  mm/memcontrol.c |  118 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 117 insertions(+), 1 deletion(-)
> 
> Index: softlimit-test2/mm/memcontrol.c
> ===================================================================
> --- softlimit-test2.orig/mm/memcontrol.c
> +++ softlimit-test2/mm/memcontrol.c
> @@ -192,7 +192,14 @@ struct mem_cgroup {
>  	atomic_t	refcnt;
> 
>  	unsigned int	swappiness;
> -
> +	/*
> +	 * For soft limit.
> +	 */
> +	int soft_limit_priority;
> +	struct list_head soft_limit_list[2];

Looking at the rest of the code in the patch, it is not apparent as to
why we need two list_heads/array of list_heads?

-- 
	Balbir

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