linux-kernel - Re: [PATCH 2/4] (CMA_AGGRESSIVE) Add argument hibernation to function shrink_all

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Date:	Thu, 16 Oct 2014 10:45:21 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Hui Zhu <zhuhui@...omi.com>
Cc:	m.szyprowski@...sung.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 2/4] (CMA_AGGRESSIVE) Add argument hibernation to function shrink_all_memory

[CC list trimmed]

On Thursday, October 16, 2014 11:35:49 AM Hui Zhu wrote:
> Function shrink_all_memory try to free `nr_to_reclaim' of memory.
> CMA_AGGRESSIVE_SHRINK function will call this functon to free `nr_to_reclaim' of
> memory.  It need different scan_control with current caller function
> hibernate_preallocate_memory.
> 
> If hibernation is true, the caller is hibernate_preallocate_memory.
> if not, the caller is CMA alloc function.
> 
> Signed-off-by: Hui Zhu <zhuhui@...omi.com>
> ---
>  include/linux/swap.h    |  3 ++-
>  kernel/power/snapshot.c |  2 +-
>  mm/vmscan.c             | 19 +++++++++++++------
>  3 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 37a585b..9f2cb43 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -335,7 +335,8 @@ extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
>  						gfp_t gfp_mask, bool noswap,
>  						struct zone *zone,
>  						unsigned long *nr_scanned);
> -extern unsigned long shrink_all_memory(unsigned long nr_pages);
> +extern unsigned long shrink_all_memory(unsigned long nr_pages,
> +				       bool hibernation);
>  extern int vm_swappiness;
>  extern int remove_mapping(struct address_space *mapping, struct page *page);
>  extern unsigned long vm_total_pages;
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index 791a618..a00fc35 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1657,7 +1657,7 @@ int hibernate_preallocate_memory(void)
>  	 * NOTE: If this is not done, performance will be hurt badly in some
>  	 * test cases.
>  	 */
> -	shrink_all_memory(saveable - size);
> +	shrink_all_memory(saveable - size, true);

Instead of doing this, can you please define

__shrink_all_memory()

that will take the appropriate struct scan_control as an argument and
then define two wrappers around that, one for hibernation and one for CMA?

The way you did it opens a field for bugs caused by passing a wrong value
as the second argument.

>  
>  	/*
>  	 * The number of saveable pages in memory was too high, so apply some
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index dcb4707..fdcfa30 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3404,7 +3404,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
>  	wake_up_interruptible(&pgdat->kswapd_wait);
>  }
>  
> -#ifdef CONFIG_HIBERNATION
> +#if defined CONFIG_HIBERNATION || defined CONFIG_CMA_AGGRESSIVE
>  /*
>   * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
>   * freed pages.
> @@ -3413,22 +3413,29 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
>   * LRU order by reclaiming preferentially
>   * inactive > active > active referenced > active mapped
>   */
> -unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
> +unsigned long shrink_all_memory(unsigned long nr_to_reclaim, bool hibernation)
>  {
>  	struct reclaim_state reclaim_state;
>  	struct scan_control sc = {
>  		.nr_to_reclaim = nr_to_reclaim,
> -		.gfp_mask = GFP_HIGHUSER_MOVABLE,
>  		.priority = DEF_PRIORITY,
> -		.may_writepage = 1,
>  		.may_unmap = 1,
>  		.may_swap = 1,
> -		.hibernation_mode = 1,
>  	};
>  	struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
>  	struct task_struct *p = current;
>  	unsigned long nr_reclaimed;
>  
> +	if (hibernation) {
> +		sc.hibernation_mode = 1;
> +		sc.may_writepage = 1;
> +		sc.gfp_mask = GFP_HIGHUSER_MOVABLE;
> +	} else {
> +		sc.hibernation_mode = 0;
> +		sc.may_writepage = !laptop_mode;
> +		sc.gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_HIGHMEM;
> +	}
> +
>  	p->flags |= PF_MEMALLOC;
>  	lockdep_set_current_reclaim_state(sc.gfp_mask);
>  	reclaim_state.reclaimed_slab = 0;
> @@ -3442,7 +3449,7 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
>  
>  	return nr_reclaimed;
>  }
> -#endif /* CONFIG_HIBERNATION */
> +#endif /* CONFIG_HIBERNATION || CONFIG_CMA_AGGRESSIVE */
>  
>  /* It's optimal to keep kswapds on the same CPUs as their memory, but
>     not required for correctness.  So if the last cpu in a node goes
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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