Re: [PATCH net-next v10 3/4] page_pool: support unlimited number of inflight pages

[Simon Horman <horms@kernel.org>]

On Wed, Feb 26, 2025 at 07:03:38PM +0800, Yunsheng Lin wrote:
> Currently a fixed size of pre-allocated memory is used to
> keep track of the inflight pages, in order to use the DMA
> API correctly.
> 
> As mentioned [1], the number of inflight pages can be up to
> 73203 depending on the use cases. Allocate memory dynamically
> to keep track of the inflight pages when pre-allocated memory
> runs out.
> 
> The overhead of using dynamic memory allocation is about 10ns~
> 20ns, which causes 5%~10% performance degradation for the test
> case of time_bench_page_pool03_slow() in [2].
> 
> 1. https://lore.kernel.org/all/b8b7818a-e44b-45f5-91c2-d5eceaa5dd5b@kernel.org/
> 2. https://github.com/netoptimizer/prototype-kernel
> CC: Robin Murphy <robin.murphy@arm.com>
> CC: Alexander Duyck <alexander.duyck@gmail.com>
> CC: IOMMU <iommu@lists.linux.dev>
> Fixes: f71fec47c2df ("page_pool: make sure struct device is stable")
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
> ---
>  Documentation/netlink/specs/netdev.yaml | 16 +++++
>  include/net/page_pool/types.h           | 10 ++++
>  include/uapi/linux/netdev.h             |  2 +
>  net/core/page_pool.c                    | 79 ++++++++++++++++++++++++-
>  net/core/page_pool_priv.h               |  2 +
>  net/core/page_pool_user.c               | 39 ++++++++++--
>  tools/net/ynl/samples/page-pool.c       | 11 ++++
>  7 files changed, 154 insertions(+), 5 deletions(-)

Hi,

It looks like the header changes in this patch don't quite
correspond to the spec changes.

But if so, perhaps the spec update needs to change,
because adding values to an enum, other than at the end,
feels like UAPI breakage to me.

I see this:

$ ./tools/net/ynl/ynl-regen.sh -f
$ git diff
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 9309cbfeb8d2..9e02f6190b07 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -100,11 +100,11 @@ enum {
 	NETDEV_A_PAGE_POOL_NAPI_ID,
 	NETDEV_A_PAGE_POOL_INFLIGHT,
 	NETDEV_A_PAGE_POOL_INFLIGHT_MEM,
+	NETDEV_A_PAGE_POOL_ITEM_MEM_RESIDENT,
+	NETDEV_A_PAGE_POOL_ITEM_MEM_USED,
 	NETDEV_A_PAGE_POOL_DETACH_TIME,
 	NETDEV_A_PAGE_POOL_DMABUF,
 	NETDEV_A_PAGE_POOL_IO_URING,
-	NETDEV_A_PAGE_POOL_ITEM_MEM_RESIDENT,
-	NETDEV_A_PAGE_POOL_ITEM_MEM_USED,
 
 	__NETDEV_A_PAGE_POOL_MAX,
 	NETDEV_A_PAGE_POOL_MAX = (__NETDEV_A_PAGE_POOL_MAX - 1)
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index 7600bf62dbdf..9e02f6190b07 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -100,6 +100,8 @@ enum {
 	NETDEV_A_PAGE_POOL_NAPI_ID,
 	NETDEV_A_PAGE_POOL_INFLIGHT,
 	NETDEV_A_PAGE_POOL_INFLIGHT_MEM,
+	NETDEV_A_PAGE_POOL_ITEM_MEM_RESIDENT,
+	NETDEV_A_PAGE_POOL_ITEM_MEM_USED,
 	NETDEV_A_PAGE_POOL_DETACH_TIME,
 	NETDEV_A_PAGE_POOL_DMABUF,
 	NETDEV_A_PAGE_POOL_IO_URING,