Hi Liang,
On Thu, 30 Nov 2023 at 13:59, Liang Chen <liangchen.linux@xxxxxxxxx> wrote:
To support multiple users referencing the same fragment, pp_frag_count is
renamed to pp_ref_count to better reflect its actual meaning based on the
suggestion from [1].
The patch does more than what the description says and those should be in 2 different patches.
I am ok with pp_frag_count -> pp_ref_count, for the functions I am not the rename makes anything better.
Jakub are you ok with the name changes or is it going to make bisecting a pain?
Thanks
/Ilias
[1]
http://lore.kernel.org/netdev/f71d9448-70c8-8793-dc9a-0eb48a570300@xxxxxxxxxx
Signed-off-by: Liang Chen <liangchen.linux@xxxxxxxxx>
Reviewed-by: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
---
.../net/ethernet/mellanox/mlx5/core/en_rx.c | 4 +-
include/linux/mm_types.h | 2 +-
include/net/page_pool/helpers.h | 45 ++++++++++---------
include/net/page_pool/types.h | 6 +--
net/core/page_pool.c | 12 ++---
5 files changed, 37 insertions(+), 32 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 8d9743a5e42c..98d33ac7ec64 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -298,8 +298,8 @@ static void mlx5e_page_release_fragmented(struct mlx5e_rq *rq,
u16 drain_count = MLX5E_PAGECNT_BIAS_MAX - frag_page->frags;
struct page *page = frag_page->page;
- if (page_pool_defrag_page(page, drain_count) == 0)
- page_pool_put_defragged_page(rq->page_pool, page, -1, true);
+ if (page_pool_unref_page(page, drain_count) == 0)
+ page_pool_put_unrefed_page(rq->page_pool, page, -1, true);
}
static inline int mlx5e_get_rx_frag(struct mlx5e_rq *rq,
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 957ce38768b2..64e4572ef06d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -125,7 +125,7 @@ struct page {
struct page_pool *pp;
unsigned long _pp_mapping_pad;
unsigned long dma_addr;
- atomic_long_t pp_frag_count;
+ atomic_long_t pp_ref_count;
};
struct { /* Tail pages of compound page */
unsigned long compound_head; /* Bit zero is set */
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 4ebd544ae977..9dc8eaf8a959 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -29,7 +29,7 @@
* page allocated from page pool. Page splitting enables memory saving and thus
* avoids TLB/cache miss for data access, but there also is some cost to
* implement page splitting, mainly some cache line dirtying/bouncing for
- * 'struct page' and atomic operation for page->pp_frag_count.
+ * 'struct page' and atomic operation for page->pp_ref_count.
*
* The API keeps track of in-flight pages, in order to let API users know when
* it is safe to free a page_pool object, the API users must call
@@ -214,69 +214,74 @@ inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
return pool->p.dma_dir;
}
-/* pp_frag_count represents the number of writers who can update the page
+/* pp_ref_count represents the number of writers who can update the page
* either by updating skb->data or via DMA mappings for the device.
* We can't rely on the page refcnt for that as we don't know who might be
* holding page references and we can't reliably destroy or sync DMA mappings
* of the fragments.
*
- * When pp_frag_count reaches 0 we can either recycle the page if the page
+ * pp_ref_count initially corresponds to the number of fragments. However,
+ * when multiple users start to reference a single fragment, for example in
+ * skb_try_coalesce, the pp_ref_count will become greater than the number of
+ * fragments.
+ *
+ * When pp_ref_count reaches 0 we can either recycle the page if the page
* refcnt is 1 or return it back to the memory allocator and destroy any
* mappings we have.
*/
static inline void page_pool_fragment_page(struct page *page, long nr)
{
- atomic_long_set(&page->pp_frag_count, nr);
+ atomic_long_set(&page->pp_ref_count, nr);
}
-static inline long page_pool_defrag_page(struct page *page, long nr)
+static inline long page_pool_unref_page(struct page *page, long nr)
{
long ret;
- /* If nr == pp_frag_count then we have cleared all remaining
+ /* If nr == pp_ref_count then we have cleared all remaining
* references to the page:
* 1. 'n == 1': no need to actually overwrite it.
* 2. 'n != 1': overwrite it with one, which is the rare case
- * for pp_frag_count draining.
+ * for pp_ref_count draining.
*
* The main advantage to doing this is that not only we avoid a atomic
* update, as an atomic_read is generally a much cheaper operation than
* an atomic update, especially when dealing with a page that may be
- * partitioned into only 2 or 3 pieces; but also unify the pp_frag_count
+ * referenced by only 2 or 3 users; but also unify the pp_ref_count
* handling by ensuring all pages have partitioned into only 1 piece
* initially, and only overwrite it when the page is partitioned into
* more than one piece.
*/
- if (atomic_long_read(&page->pp_frag_count) == nr) {
+ if (atomic_long_read(&page->pp_ref_count) == nr) {
/* As we have ensured nr is always one for constant case using
* the BUILD_BUG_ON(), only need to handle the non-constant case
- * here for pp_frag_count draining, which is a rare case.
+ * here for pp_ref_count draining, which is a rare case.
*/
BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1);
if (!__builtin_constant_p(nr))
- atomic_long_set(&page->pp_frag_count, 1);
+ atomic_long_set(&page->pp_ref_count, 1);
return 0;
}
- ret = atomic_long_sub_return(nr, &page->pp_frag_count);
+ ret = atomic_long_sub_return(nr, &page->pp_ref_count);
WARN_ON(ret < 0);
- /* We are the last user here too, reset pp_frag_count back to 1 to
+ /* We are the last user here too, reset pp_ref_count back to 1 to
* ensure all pages have been partitioned into 1 piece initially,
* this should be the rare case when the last two fragment users call
- * page_pool_defrag_page() currently.
+ * page_pool_unref_page() currently.
*/
if (unlikely(!ret))
- atomic_long_set(&page->pp_frag_count, 1);
+ atomic_long_set(&page->pp_ref_count, 1);
return ret;
}
-static inline bool page_pool_is_last_frag(struct page *page)
+static inline bool page_pool_is_last_ref(struct page *page)
{
- /* If page_pool_defrag_page() returns 0, we were the last user */
- return page_pool_defrag_page(page, 1) == 0;
+ /* If page_pool_unref_page() returns 0, we were the last user */
+ return page_pool_unref_page(page, 1) == 0;
}
/**
@@ -301,10 +306,10 @@ static inline void page_pool_put_page(struct page_pool *pool,
* allow registering MEM_TYPE_PAGE_POOL, but shield linker.
*/
#ifdef CONFIG_PAGE_POOL
- if (!page_pool_is_last_frag(page))
+ if (!page_pool_is_last_ref(page))
return;
- page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct);
+ page_pool_put_unrefed_page(pool, page, dma_sync_size, allow_direct);
#endif
}
diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index e1bb92c192de..6a5323619f6e 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -224,9 +224,9 @@ static inline void page_pool_put_page_bulk(struct page_pool *pool, void **data,
}
#endif
-void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
- unsigned int dma_sync_size,
- bool allow_direct);
+void page_pool_put_unrefed_page(struct page_pool *pool, struct page *page,
+ unsigned int dma_sync_size,
+ bool allow_direct);
static inline bool is_page_pool_compiled_in(void)
{
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index df2a06d7da52..106220b1f89c 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -650,8 +650,8 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
return NULL;
}
-void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
- unsigned int dma_sync_size, bool allow_direct)
+void page_pool_put_unrefed_page(struct page_pool *pool, struct page *page,
+ unsigned int dma_sync_size, bool allow_direct)
{
page = __page_pool_put_page(pool, page, dma_sync_size, allow_direct);
if (page && !page_pool_recycle_in_ring(pool, page)) {
@@ -660,7 +660,7 @@ void page_pool_put_defragged_page(struct page_pool *pool, struct page *page,
page_pool_return_page(pool, page);
}
}
-EXPORT_SYMBOL(page_pool_put_defragged_page);
+EXPORT_SYMBOL(page_pool_put_unrefed_page);
/**
* page_pool_put_page_bulk() - release references on multiple pages
@@ -687,7 +687,7 @@ void page_pool_put_page_bulk(struct page_pool *pool, void **data,
struct page *page = virt_to_head_page(data[i]);
/* It is not the last user for the page frag case */
- if (!page_pool_is_last_frag(page))
+ if (!page_pool_is_last_ref(page))
continue;
page = __page_pool_put_page(pool, page, -1, false);
@@ -729,7 +729,7 @@ static struct page *page_pool_drain_frag(struct page_pool *pool,
long drain_count = BIAS_MAX - pool->frag_users;
/* Some user is still using the page frag */
- if (likely(page_pool_defrag_page(page, drain_count)))
+ if (likely(page_pool_unref_page(page, drain_count)))
return NULL;
if (page_ref_count(page) == 1 && !page_is_pfmemalloc(page)) {
@@ -750,7 +750,7 @@ static void page_pool_free_frag(struct page_pool *pool)
pool->frag_page = NULL;
- if (!page || page_pool_defrag_page(page, drain_count))
+ if (!page || page_pool_unref_page(page, drain_count))
return;
page_pool_return_page(pool, page);
--
2.31.1
