[Linaro-mm-sig] Re: [PATCH] udmabuf: use kmem_cache to alloc udmabuf folio

On Wed, Jul 31, 2024 at 11:34:49AM +0800, Huan Yang wrote:

The current udmabuf_folio contains a list_head and the corresponding folio pointer, with a size of 24 bytes. udmabuf_folio uses kmalloc to allocate memory.

However, kmalloc is a public pool, starting from 64 bytes. This means that each udmabuf_folio allocation will waste 40 bytes.

Considering that each udmabuf creates a folio corresponding to a udmabuf_folio, the wasted memory can be significant in the case of memory fragmentation.

Furthermore, if udmabuf is frequently used, the allocation and deallocation of udmabuf_folio will also be frequent.

Therefore, this patch adds a kmem_cache dedicated to the allocation and deallocation of udmabuf_folio.This is expected to improve the performance of allocation and deallocation within the expected range, while also avoiding memory waste.

Signed-off-by: Huan Yang link@vivo.com

drivers/dma-buf/udmabuf.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index 047c3cd2ceff..db4de8c745ce 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -24,6 +24,8 @@ static int size_limit_mb = 64; module_param(size_limit_mb, int, 0644); MODULE_PARM_DESC(size_limit_mb, "Max size of a dmabuf, in megabytes. Default is 64."); +static struct kmem_cache *udmabuf_folio_cachep;

struct udmabuf { pgoff_t pagecount; struct folio **folios; @@ -169,7 +171,7 @@ static void unpin_all_folios(struct list_head *unpin_list) unpin_folio(ubuf_folio->folio); list_del(&ubuf_folio->list);

• kfree(ubuf_folio);
  

• kmem_cache_free(udmabuf_folio_cachep, ubuf_folio);
  

  }

} @@ -178,7 +180,7 @@ static int add_to_unpin_list(struct list_head *unpin_list, { struct udmabuf_folio *ubuf_folio;

• ubuf_folio = kzalloc(sizeof(*ubuf_folio), GFP_KERNEL);

• ubuf_folio = kmem_cache_alloc(udmabuf_folio_cachep, GFP_KERNEL); if (!ubuf_folio) return -ENOMEM;

@@ -492,10 +494,20 @@ static int __init udmabuf_dev_init(void) if (ret < 0) { pr_err("Could not setup DMA mask for udmabuf device\n"); misc_deregister(&udmabuf_misc);

misc_deregister() is now called twice in this error path, I think you've forgotten to delete this line too?

Otherwise lgtm. -Sima

• return ret;
  

• goto err;
  

• }
• udmabuf_folio_cachep = KMEM_CACHE(udmabuf_folio, 0);
• if (unlikely(!udmabuf_folio_cachep)) {

• ret = -ENOMEM;
  

• goto err;
  

  }

return 0;

+err:

• misc_deregister(&udmabuf_misc);
• return ret;

} static void __exit udmabuf_dev_exit(void)

base-commit: cd19ac2f903276b820f5d0d89de0c896c27036ed

2.45.2