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@xxxxxxxx>
> ---
> 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
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
