[PATCH net-next v3 0/3] skbuff: Optimize SKB coalescing for page pool

[PATCH net-next v3 0/3] skbuff: Optimize SKB coalescing for page pool

[Liang Chen]

The combination of the following condition was excluded from skb coalescing:

from->pp_recycle = 1
from->cloned = 1
to->pp_recycle = 1

With page pool in use, this combination can be quite common(ex.
NetworkMananger may lead to the additional packet_type being registered,
thus the cloning). In scenarios with a higher number of small packets, it
can significantly affect the success rate of coalescing.

This patchset aims to optimize this scenario and enable coalescing of this
particular combination. That also involves supporting multiple users
referencing the same fragment of a pp page to accomondate the need to
increment the "from" SKB page's pp page reference count.


Changes from v2:
- rename a few other functions leaning more towards pp_ref_count managing

Liang Chen (3):
  page_pool: Rename pp_frag_count to pp_ref_count
  page_pool: halve BIAS_MAX for fragment multiple user references
  skbuff: Optimization of SKB coalescing for page pool

 .../net/ethernet/mellanox/mlx5/core/en_rx.c   |  4 +-
 include/linux/mm_types.h                      |  2 +-
 include/net/page_pool/helpers.h               | 67 +++++++++++++------
 include/net/page_pool/types.h                 |  2 +-
 net/core/page_pool.c                          | 14 ++--
 net/core/skbuff.c                             | 23 +++----
 6 files changed, 69 insertions(+), 43 deletions(-)

-- 
2.31.1

[PATCH net-next v3 1/3] page_pool: Rename pp_frag_count to pp_ref_count

[Liang Chen]

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].

[1]
http://lore.kernel.org/netdev/f71d9448-70c8-8793-dc9a-0eb48a570300@huawei.com

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
---
 .../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                 |  2 +-
 net/core/page_pool.c                          | 12 ++---
 5 files changed, 35 insertions(+), 30 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..4454c750733e 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_deref_page(page, drain_count) == 0)
+		page_pool_put_derefed_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..700f435292e7 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_deref_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_deref_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_deref_page() returns 0, we were the last user */
+	return page_pool_deref_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_derefed_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..1c82e87f2577 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h
@@ -224,7 +224,7 @@ 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,
+void page_pool_put_derefed_page(struct page_pool *pool, struct page *page,
 				  unsigned int dma_sync_size,
 				  bool allow_direct);
 
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index df2a06d7da52..0c6c2b11aabe 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_derefed_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_derefed_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_deref_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_deref_page(page, drain_count))
 		return;
 
 	page_pool_return_page(pool, page);
-- 
2.31.1

Re: [PATCH net-next v3 1/3] page_pool: Rename pp_frag_count to pp_ref_count

[Yunsheng Lin]

On 2023/11/24 15:34, Liang Chen wrote:

>  static inline void page_pool_fragment_page(struct page *page, long nr)

It seems page_pool_fragment_page() might not be a appropriate name too?

Perhaps it might be better to grep defrag/frag to see if there is other
function name might need changing.

>  {
> -	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_deref_page(struct page *page, long nr)

page_pool_defrag_page() related function is called by mlx5 driver directly,
we need to change it to use the new function too.

I assume that deref is short for dereference? According to:

https://stackoverflow.com/questions/4955198/what-does-dereferencing-a-pointer-mean-in-c-c

'dereferencing means accessing the value from a certain memory location
against which that pointer is pointing'.

So I am not sure if 'deref' is the right word here as I am not a native
english speaker, But it seems 'unref' is more appropriate here if we mirror
the napi_frag_unref() function name?

Re: [PATCH net-next v3 1/3] page_pool: Rename pp_frag_count to pp_ref_count

[Liang Chen]

On Sat, Nov 25, 2023 at 7:53 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> On 2023/11/24 15:34, Liang Chen wrote:
>
> >  static inline void page_pool_fragment_page(struct page *page, long nr)
>
> It seems page_pool_fragment_page() might not be a appropriate name too?
>
> Perhaps it might be better to grep defrag/frag to see if there is other
> function name might need changing.
>

Our understanding is that the concept of fragmenting exists before the
page is drained, and all related functions should retain their current
names. However, once the page is drained, its management shifts to
being governed by pp_ref_count, and there's no longer a need to
consider fragmentation. Therefore, all functions associated with that
lifecycle stage of a pp page will be renamed. With that in mind, the
following functions have been renamed.

page_pool_defrag_page -> page_pool_deref_page
page_pool_is_last_frag -> page_pool_is_last_ref
page_pool_put_defragged_page -> page_pool_put_derefed_page

> >  {
> > -     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_deref_page(struct page *page, long nr)
>
> page_pool_defrag_page() related function is called by mlx5 driver directly,
> we need to change it to use the new function too.
>

Yeah, that change is right at the start of the patch.

> I assume that deref is short for dereference? According to:
>
> https://stackoverflow.com/questions/4955198/what-does-dereferencing-a-pointer-mean-in-c-c
>
> 'dereferencing means accessing the value from a certain memory location
> against which that pointer is pointing'.
>
> So I am not sure if 'deref' is the right word here as I am not a native
> english speaker, But it seems 'unref' is more appropriate here if we mirror
> the napi_frag_unref() function name?

That sounds better to me as well. Thanks!

[PATCH net-next v3 2/3] page_pool: halve BIAS_MAX for fragment multiple user references

[Liang Chen]

Referring to patch [1], in order to support multiple users referencing the
same fragment and prevent overflow from pp_ref_count growing, the initial
value of pp_ref_count is halved, leaving room for pp_ref_count to increment
before the page is drained.

[1]
https://lore.kernel.org/all/20211009093724.10539-3-linyunsheng@huawei.com/

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
---
 net/core/page_pool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 0c6c2b11aabe..24b83dfe6968 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -26,7 +26,7 @@
 #define DEFER_TIME (msecs_to_jiffies(1000))
 #define DEFER_WARN_INTERVAL (60 * HZ)
 
-#define BIAS_MAX	LONG_MAX
+#define BIAS_MAX	(LONG_MAX >> 1)
 
 #ifdef CONFIG_PAGE_POOL_STATS
 /* alloc_stat_inc is intended to be used in softirq context */
-- 
2.31.1

Re: [PATCH net-next v3 2/3] page_pool: halve BIAS_MAX for fragment multiple user references

[Yunsheng Lin]

On 2023/11/24 15:34, Liang Chen wrote:

The title seems a little hard for me to understand, but the description
below does seem clear to me, so LGTM.

Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>

> Referring to patch [1], in order to support multiple users referencing the
> same fragment and prevent overflow from pp_ref_count growing, the initial
> value of pp_ref_count is halved, leaving room for pp_ref_count to increment
> before the page is drained.

Re: [PATCH net-next v3 2/3] page_pool: halve BIAS_MAX for fragment multiple user references

[Liang Chen]

On Sat, Nov 25, 2023 at 8:01 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> On 2023/11/24 15:34, Liang Chen wrote:
>
> The title seems a little hard for me to understand, but the description
> below does seem clear to me, so LGTM.
>
> Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
>

Thanks! I will change the title to "halve BIAS_MAX for multiple user
references of a fragment"


> > Referring to patch [1], in order to support multiple users referencing the
> > same fragment and prevent overflow from pp_ref_count growing, the initial
> > value of pp_ref_count is halved, leaving room for pp_ref_count to increment
> > before the page is drained.

[PATCH net-next v3 3/3] skbuff: Optimization of SKB coalescing for page pool

[Liang Chen]

In order to address the issues encountered with commit 1effe8ca4e34
("skbuff: fix coalescing for page_pool fragment recycling"), the
combination of the following condition was excluded from skb coalescing:

from->pp_recycle = 1
from->cloned = 1
to->pp_recycle = 1

However, with page pool environments, the aforementioned combination can
be quite common(ex. NetworkMananger may lead to the additional
packet_type being registered, thus the cloning). In scenarios with a
higher number of small packets, it can significantly affect the success
rate of coalescing. For example, considering packets of 256 bytes size,
our comparison of coalescing success rate is as follows:

Without page pool: 70%
With page pool: 13%

Consequently, this has an impact on performance:

Without page pool: 2.57 Gbits/sec
With page pool: 2.26 Gbits/sec

Therefore, it seems worthwhile to optimize this scenario and enable
coalescing of this particular combination. To achieve this, we need to
ensure the correct increment of the "from" SKB page's page pool
reference count (pp_ref_count).

Following this optimization, the success rate of coalescing measured in
our environment has improved as follows:

With page pool: 60%

This success rate is approaching the rate achieved without using page
pool, and the performance has also been improved:

With page pool: 2.52 Gbits/sec

Below is the performance comparison for small packets before and after
this optimization. We observe no impact to packets larger than 4K.

packet size     before      after       improved
(bytes)         (Gbits/sec) (Gbits/sec)
128             1.19        1.27        7.13%
256             2.26        2.52        11.75%
512             4.13        4.81        16.50%
1024            6.17        6.73        9.05%
2048            14.54       15.47       6.45%
4096            25.44       27.87       9.52%

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
---
 include/net/page_pool/helpers.h | 22 ++++++++++++++++++++++
 net/core/skbuff.c               | 23 +++++++++++------------
 2 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 700f435292e7..6b3c0d4d47f5 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -402,4 +402,26 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
 		page_pool_update_nid(pool, new_nid);
 }
 
+static inline bool page_pool_is_pp_page(struct page *page)
+{
+	return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
+}
+
+/**
+ * page_pool_get_frag_ref() - Increase fragment reference count of a page
+ * @page:	page of the fragment on which to increase a reference
+ *
+ * Increase fragment reference count (pp_ref_count) on a page, but if it is
+ * not a page pool page, fallback to increase a reference(_refcount) on a
+ * normal page.
+ */
+static inline void page_pool_get_frag_ref(struct page *page)
+{
+	struct page *head_page = compound_head(page);
+
+	if (likely(page_pool_is_pp_page(head_page)))
+		atomic_long_inc(&head_page->pp_ref_count);
+	else
+		get_page(head_page);
+}
 #endif /* _NET_PAGE_POOL_HELPERS_H */
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b157efea5dea..54e6945ead56 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5764,17 +5764,12 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 		return false;
 
 	/* In general, avoid mixing page_pool and non-page_pool allocated
-	 * pages within the same SKB. Additionally avoid dealing with clones
-	 * with page_pool pages, in case the SKB is using page_pool fragment
-	 * references (page_pool_alloc_frag()). Since we only take full page
-	 * references for cloned SKBs at the moment that would result in
-	 * inconsistent reference counts.
-	 * In theory we could take full references if @from is cloned and
-	 * !@to->pp_recycle but its tricky (due to potential race with
-	 * the clone disappearing) and rare, so not worth dealing with.
+	 * pages within the same SKB. In theory we could take full
+	 * references if @from is cloned and !@to->pp_recycle but its
+	 * tricky (due to potential race with the clone disappearing) and
+	 * rare, so not worth dealing with.
 	 */
-	if (to->pp_recycle != from->pp_recycle ||
-	    (from->pp_recycle && skb_cloned(from)))
+	if (to->pp_recycle != from->pp_recycle)
 		return false;
 
 	if (len <= skb_tailroom(to)) {
@@ -5831,8 +5826,12 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 	/* if the skb is not cloned this does nothing
 	 * since we set nr_frags to 0.
 	 */
-	for (i = 0; i < from_shinfo->nr_frags; i++)
-		__skb_frag_ref(&from_shinfo->frags[i]);
+	if (from->pp_recycle)
+		for (i = 0; i < from_shinfo->nr_frags; i++)
+			page_pool_get_frag_ref(skb_frag_page(&from_shinfo->frags[i]));
+	else
+		for (i = 0; i < from_shinfo->nr_frags; i++)
+			__skb_frag_ref(&from_shinfo->frags[i]);
 
 	to->truesize += delta;
 	to->len += len;
-- 
2.31.1

Re: [PATCH net-next v3 3/3] skbuff: Optimization of SKB coalescing for page pool

[Yunsheng Lin]

On 2023/11/24 15:34, Liang Chen wrote:

...

> --- a/include/net/page_pool/helpers.h
> +++ b/include/net/page_pool/helpers.h
> @@ -402,4 +402,26 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
>  		page_pool_update_nid(pool, new_nid);
>  }
>
> +static inline bool page_pool_is_pp_page(struct page *page)
> +{

We have a page->pp_magic checking in napi_pp_put_page() in skbuff.c already,
it seems better to move it to skbuff.c or skbuff.h and use it for
napi_pp_put_page() too, as we seem to have chosen to demux the page_pool
owned page and non-page_pool owned page handling in the skbuff core.

If we move it to skbuff.c or skbuff.h, we might need a better prefix than
page_pool_* too.

Re: [PATCH net-next v3 3/3] skbuff: Optimization of SKB coalescing for page pool

[Liang Chen]

On Sat, Nov 25, 2023 at 8:16 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> On 2023/11/24 15:34, Liang Chen wrote:
>
> ...
>
> > --- a/include/net/page_pool/helpers.h
> > +++ b/include/net/page_pool/helpers.h
> > @@ -402,4 +402,26 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
> >               page_pool_update_nid(pool, new_nid);
> >  }
> >
> > +static inline bool page_pool_is_pp_page(struct page *page)
> > +{
>
> We have a page->pp_magic checking in napi_pp_put_page() in skbuff.c already,
> it seems better to move it to skbuff.c or skbuff.h and use it for
> napi_pp_put_page() too, as we seem to have chosen to demux the page_pool
> owned page and non-page_pool owned page handling in the skbuff core.
>
> If we move it to skbuff.c or skbuff.h, we might need a better prefix than
> page_pool_* too.
>

How about keeping the 'page_pool_is_pp_page' function in 'helper.h'
and letting 'skbbuff.c' use it? It seems like the function's logic is
better suited to be internal to the page pool, and it might be needed
outside of 'skbuff.c' in the future.

Re: [PATCH net-next v3 3/3] skbuff: Optimization of SKB coalescing for page pool

[Yunsheng Lin]

On 2023/11/27 12:23, Liang Chen wrote:
> On Sat, Nov 25, 2023 at 8:16 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
>>
>> On 2023/11/24 15:34, Liang Chen wrote:
>>
>> ...
>>
>>> --- a/include/net/page_pool/helpers.h
>>> +++ b/include/net/page_pool/helpers.h
>>> @@ -402,4 +402,26 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
>>>               page_pool_update_nid(pool, new_nid);
>>>  }
>>>
>>> +static inline bool page_pool_is_pp_page(struct page *page)
>>> +{
>>
>> We have a page->pp_magic checking in napi_pp_put_page() in skbuff.c already,
>> it seems better to move it to skbuff.c or skbuff.h and use it for
>> napi_pp_put_page() too, as we seem to have chosen to demux the page_pool
>> owned page and non-page_pool owned page handling in the skbuff core.
>>
>> If we move it to skbuff.c or skbuff.h, we might need a better prefix than
>> page_pool_* too.
>>
> 
> How about keeping the 'page_pool_is_pp_page' function in 'helper.h'
> and letting 'skbbuff.c' use it? It seems like the function's logic is
> better suited to be internal to the page pool, and it might be needed
> outside of 'skbuff.c' in the future.

Yes, we can always extend it outside of 'skbuff' if there is a need in
the future.

For now, maybe it makes more sense to export as litte as possible in the
.h file mirroring the napi_pp_put_page().

> .
> 

Re: [PATCH net-next v3 3/3] skbuff: Optimization of SKB coalescing for page pool

[Liang Chen]

On Mon, Nov 27, 2023 at 6:48 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
>
> On 2023/11/27 12:23, Liang Chen wrote:
> > On Sat, Nov 25, 2023 at 8:16 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
> >>
> >> On 2023/11/24 15:34, Liang Chen wrote:
> >>
> >> ...
> >>
> >>> --- a/include/net/page_pool/helpers.h
> >>> +++ b/include/net/page_pool/helpers.h
> >>> @@ -402,4 +402,26 @@ static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
> >>>               page_pool_update_nid(pool, new_nid);
> >>>  }
> >>>
> >>> +static inline bool page_pool_is_pp_page(struct page *page)
> >>> +{
> >>
> >> We have a page->pp_magic checking in napi_pp_put_page() in skbuff.c already,
> >> it seems better to move it to skbuff.c or skbuff.h and use it for
> >> napi_pp_put_page() too, as we seem to have chosen to demux the page_pool
> >> owned page and non-page_pool owned page handling in the skbuff core.
> >>
> >> If we move it to skbuff.c or skbuff.h, we might need a better prefix than
> >> page_pool_* too.
> >>
> >
> > How about keeping the 'page_pool_is_pp_page' function in 'helper.h'
> > and letting 'skbbuff.c' use it? It seems like the function's logic is
> > better suited to be internal to the page pool, and it might be needed
> > outside of 'skbuff.c' in the future.
>
> Yes, we can always extend it outside of 'skbuff' if there is a need in
> the future.
>
> For now, maybe it makes more sense to export as litte as possible in the
> .h file mirroring the napi_pp_put_page().
>

Sure. will be done in v4. Thanks!

> > .
> >