Re: [PATCH] driver : staging : ion: optimization for decreasing memory fragmentaion

[David Rientjes <rientjes@google.com>]

On Thu, 14 Mar 2019, Zhaoyang Huang wrote:

> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> 
> Two action for this patch:
> 1. set a batch size for system heap's shrinker, which can have it buffer
> reasonable page blocks in pool for future allocation.
> 2. reverse the order sequence when free page blocks, the purpose is also
> to have system heap keep as more big blocks as it can.
> 
> By testing on an android system with 2G RAM, the changes with setting
> batch = 48MB can help reduce the fragmentation obviously and improve
> big block allocation speed for 15%.
> 
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
>  drivers/staging/android/ion/ion_heap.c        | 12 +++++++++++-
>  drivers/staging/android/ion/ion_system_heap.c |  2 +-
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/android/ion/ion_heap.c b/drivers/staging/android/ion/ion_heap.c
> index 31db510..9e9caf2 100644
> --- a/drivers/staging/android/ion/ion_heap.c
> +++ b/drivers/staging/android/ion/ion_heap.c
> @@ -16,6 +16,8 @@
>  #include <linux/vmalloc.h>
>  #include "ion.h"
>  
> +unsigned long ion_heap_batch = 0;

static?

> +
>  void *ion_heap_map_kernel(struct ion_heap *heap,
>  			  struct ion_buffer *buffer)
>  {
> @@ -303,7 +305,15 @@ int ion_heap_init_shrinker(struct ion_heap *heap)
>  	heap->shrinker.count_objects = ion_heap_shrink_count;
>  	heap->shrinker.scan_objects = ion_heap_shrink_scan;
>  	heap->shrinker.seeks = DEFAULT_SEEKS;
> -	heap->shrinker.batch = 0;
> +	heap->shrinker.batch = ion_heap_batch;
>  
>  	return register_shrinker(&heap->shrinker);
>  }
> +
> +static int __init ion_system_heap_batch_init(char *arg)
> +{
> +	 ion_heap_batch = memparse(arg, NULL);
> +

No bounds checking?  What are the legitimate upper and lower bounds here?

> +	return 0;
> +}
> +early_param("ion_batch", ion_system_heap_batch_init);
> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> index 701eb9f..d249f8d 100644
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -182,7 +182,7 @@ static int ion_system_heap_shrink(struct ion_heap *heap, gfp_t gfp_mask,
>  	if (!nr_to_scan)
>  		only_scan = 1;
>  
> -	for (i = 0; i < NUM_ORDERS; i++) {
> +	for (i = NUM_ORDERS - 1; i >= 0; i--) {
>  		pool = sys_heap->pools[i];
>  
>  		if (only_scan) {

Can we get a Documentation update on how we can use ion_batch and what the 
appropriate settings are (and in what circumstances)?