linux-kernel - Re: [PATCH] ION: Sys_heap: Makes ion buffer always alloc from page pool

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Message-ID: <572C0606.3020106@hisilicon.com>
Date:	Fri, 6 May 2016 10:48:38 +0800
From:	Chen Feng <puck.chen@...ilicon.com>
To:	Laura Abbott <labbott@...hat.com>, <yudongbin@...ilicon.com>,
	<gregkh@...uxfoundation.org>, <arve@...roid.com>,
	<riandrews@...roid.com>, <paul.gortmaker@...driver.com>,
	<bmarsh94@...il.com>, <devel@...verdev.osuosl.org>,
	<linux-kernel@...r.kernel.org>
CC:	<suzhuangluan@...ilicon.com>, <dan.zhao@...ilicon.com>,
	<zhaojunmin@...wei.com>, <xuyiping@...ilicon.com>,
	<puck.chen@...mail.com>
Subject: Re: [PATCH] ION: Sys_heap: Makes ion buffer always alloc from page
 pool



On 2016/5/6 1:09, Laura Abbott wrote:
> On 05/04/2016 08:27 PM, Chen Feng wrote:
>> Makes the ion buffer always alloced from page pool, no matter
>> it's cached or not. In this way, it can improve the efficiency
>> of it.
>>
>> Currently, there is no difference from cached or non-cached buffer
>> for the page pool.
> 
> 
> The advantage of the uncached pool was that the pages in the pool
> were always clean in the cache. This is lost here with the addition
> of cached pages to the same pool as uncached pages I agree the
> cache path could benefit from pooling but we need to keep the caching
> model consistent.
> 
Yes, the buffer in the pool is non-cached.

I found that the ion don't have a invalid cache ops.
Currently, we use ioctl to keep the cache coherency.
In this way, there is no difference between these.

So, how do you think add a new cached pool in the system heap?
If yes, I can file a new patch to do this.

>>
>> Signed-off-by: Chen Feng <puck.chen@...ilicon.com>
>> ---
>>  drivers/staging/android/ion/ion_system_heap.c | 19 ++-----------------
>>  1 file changed, 2 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
>> index b69dfc7..caf11fc 100644
>> --- a/drivers/staging/android/ion/ion_system_heap.c
>> +++ b/drivers/staging/android/ion/ion_system_heap.c
>> @@ -56,24 +56,10 @@ static struct page *alloc_buffer_page(struct ion_system_heap *heap,
>>                        struct ion_buffer *buffer,
>>                        unsigned long order)
>>  {
>> -    bool cached = ion_buffer_cached(buffer);
>>      struct ion_page_pool *pool = heap->pools[order_to_index(order)];
>>      struct page *page;
>>
>> -    if (!cached) {
>> -        page = ion_page_pool_alloc(pool);
>> -    } else {
>> -        gfp_t gfp_flags = low_order_gfp_flags;
>> -
>> -        if (order > 4)
>> -            gfp_flags = high_order_gfp_flags;
>> -        page = alloc_pages(gfp_flags | __GFP_COMP, order);
>> -        if (!page)
>> -            return NULL;
>> -        ion_pages_sync_for_device(NULL, page, PAGE_SIZE << order,
>> -                        DMA_BIDIRECTIONAL);
>> -    }
>> -
>> +    page = ion_page_pool_alloc(pool);
>>      return page;
>>  }
>>
>> @@ -81,9 +67,8 @@ static void free_buffer_page(struct ion_system_heap *heap,
>>                   struct ion_buffer *buffer, struct page *page)
>>  {
>>      unsigned int order = compound_order(page);
>> -    bool cached = ion_buffer_cached(buffer);
>>
>> -    if (!cached && !(buffer->private_flags & ION_PRIV_FLAG_SHRINKER_FREE)) {
>> +    if (!(buffer->private_flags & ION_PRIV_FLAG_SHRINKER_FREE)) {
>>          struct ion_page_pool *pool = heap->pools[order_to_index(order)];
>>
>>          ion_page_pool_free(pool, page);
>>
> 
> 
> .
>