linux-kernel - Re: [PATCHv3 1/2] staging: ion: shrink page-pool by page unit

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Message-ID: <5595812D.7050601@redhat.com>
Date:	Thu, 2 Jul 2015 11:21:33 -0700
From:	Laura Abbott <labbott@...hat.com>
To:	Gioh Kim <gioh.kim@....com>, gregkh@...uxfoundation.org,
	arve@...roid.com, riandrews@...roid.com,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 1/2] staging: ion: shrink page-pool by page unit

On 07/01/2015 04:02 AM, Gioh Kim wrote:
> This patch shrink page-pool by page unit.
>
> The system shrinker calls ion_heap_shrink_count() to get nr_to_scan,
> and pass it to ion_heap_shrink_scan().
> The problem is the return value of ion_heap_shrink_count() is the number
> of pages but ion_system_heap_shrink(), which is called by
> ion_heap_shrink_scan(), gets the number of chunk.
>
> The main root of this is that ion_page_pool_shrink() returns page count
> via ion_page_pool_total() if it have to check pool size. But it frees
> chunks of pages if it have to free pools.
>
> This patch first fix ion_page_pool_shrink() to count only pages,
> not chunks. And then ion_system_heap_shrink() to work on pages.
>
> Signed-off-by: Gioh Kim <gioh.kim@....com>

Reviewed-by: Laura Abbott <labbott@...hat.com>

> ---
>   drivers/staging/android/ion/ion_page_pool.c   |    5 +++--
>   drivers/staging/android/ion/ion_system_heap.c |   16 ++++++++++++++--
>   2 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/android/ion/ion_page_pool.c b/drivers/staging/android/ion/ion_page_pool.c
> index 4b88f11..19ad3ab 100644
> --- a/drivers/staging/android/ion/ion_page_pool.c
> +++ b/drivers/staging/android/ion/ion_page_pool.c
> @@ -116,7 +116,7 @@ static int ion_page_pool_total(struct ion_page_pool *pool, bool high)
>   int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
>   				int nr_to_scan)
>   {
> -	int freed;
> +	int freed = 0;
>   	bool high;
>
>   	if (current_is_kswapd())
> @@ -127,7 +127,7 @@ int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
>   	if (nr_to_scan == 0)
>   		return ion_page_pool_total(pool, high);
>
> -	for (freed = 0; freed < nr_to_scan; freed++) {
> +	while (freed < nr_to_scan) {
>   		struct page *page;
>
>   		mutex_lock(&pool->mutex);
> @@ -141,6 +141,7 @@ int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
>   		}
>   		mutex_unlock(&pool->mutex);
>   		ion_page_pool_free_pages(pool, page);
> +		freed += (1 << pool->order);
>   	}
>
>   	return freed;
> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> index da2a63c..7a7a9a0 100644
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -212,14 +212,26 @@ static int ion_system_heap_shrink(struct ion_heap *heap, gfp_t gfp_mask,
>   {
>   	struct ion_system_heap *sys_heap;
>   	int nr_total = 0;
> -	int i;
> +	int i, nr_freed;
> +	int only_scan = 0;
>
>   	sys_heap = container_of(heap, struct ion_system_heap, heap);
>
> +	if (!nr_to_scan)
> +		only_scan = 1;
> +
>   	for (i = 0; i < num_orders; i++) {
>   		struct ion_page_pool *pool = sys_heap->pools[i];
>
> -		nr_total += ion_page_pool_shrink(pool, gfp_mask, nr_to_scan);
> +		nr_freed = ion_page_pool_shrink(pool, gfp_mask, nr_to_scan);
> +		nr_total += nr_freed;
> +
> +		if (!only_scan) {
> +			nr_to_scan -= nr_freed;
> +			/* shrink completed */
> +			if (nr_to_scan <= 0)
> +				break;
> +		}
>   	}
>
>   	return nr_total;
>


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