[PATCH net-next v6 0/4] skbuff: Optimize SKB coalescing for page pool

[PATCH net-next v6 0/4] 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 v5:
- fix a style issue


Liang Chen (4):
  page_pool: Rename pp_frag_count to pp_ref_count
  page_pool: halve BIAS_MAX for multiple user references of a fragment
  skbuff: Add a function to check if a page belongs to page_pool
  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               | 50 +++++++++++--------
 include/net/page_pool/types.h                 |  6 +--
 net/core/page_pool.c                          | 14 +++---
 net/core/skbuff.c                             | 48 +++++++++++++-----
 6 files changed, 78 insertions(+), 46 deletions(-)

-- 
2.31.1

[PATCH net-next v6 1/4] 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>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.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                 |  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

Re: [PATCH net-next v6 1/4] page_pool: Rename pp_frag_count to pp_ref_count

[Ilias Apalodimas]

re-sending as plain-text, apologize for the noise...

On Fri, 1 Dec 2023 at 11:59, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> Hi Liang,
>
> On Thu, 30 Nov 2023 at 13:59, Liang Chen <liangchen.linux@gmail.com> 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
sure the rename makes anything better.

Jakub, are you ok with the name changes or is it going to make bisecting a pain?

Thanks
/Ilias

Re: [PATCH net-next v6 1/4] page_pool: Rename pp_frag_count to pp_ref_count

[Jakub Kicinski]

On Fri, 1 Dec 2023 12:10:10 +0200 Ilias Apalodimas wrote:
> Jakub, are you ok with the name changes or is it going to make
> bisecting a pain?

It's perfectly fine.
I should probably mention that I asked for this rename,
so I'm not impartial :)

Re: [PATCH net-next v6 1/4] page_pool: Rename pp_frag_count to pp_ref_count

[Liang Chen]

On Fri, Dec 1, 2023 at 6:10 PM Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> re-sending as plain-text, apologize for the noise...
>
> On Fri, 1 Dec 2023 at 11:59, Ilias Apalodimas
> <ilias.apalodimas@linaro.org> wrote:
> >
> > Hi Liang,
> >
> > On Thu, 30 Nov 2023 at 13:59, Liang Chen <liangchen.linux@gmail.com> 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
> sure the rename makes anything better.

Yeah, the description doesn't adequately convey what the patch does.
Before proceeding with splitting the patch, how about changing the
description to the following?

page_pool: transition to reference count management after page draining

To support multiple users referencing the same fragment,
'pp_frag_count' is renamed to 'pp_ref_count', transitioning pp pages
from fragment management to reference count management after draining
based on the suggestion from [1].

The idea is that the concept of fragmenting exists before the page is
drained, and all related functions retain their current names.
However, once the page is drained, its management shifts to being
governed by 'pp_ref_count'. Therefore, all functions associated with
that lifecycle stage of a pp page are renamed.





>
> Jakub, are you ok with the name changes or is it going to make bisecting a pain?
>
> Thanks
> /Ilias

[PATCH net-next v6 2/4] page_pool: halve BIAS_MAX for multiple user references of a fragment

[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>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.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 106220b1f89c..436f7ffea7b4 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

[PATCH net-next v6 3/4] skbuff: Add a function to check if a page belongs to page_pool

[Liang Chen]

Wrap code for checking if a page is a page_pool page into a
function for better readability and ease of reuse.

Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
---
 net/core/skbuff.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b157efea5dea..31e57c29c556 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -890,6 +890,11 @@ static void skb_clone_fraglist(struct sk_buff *skb)
 		skb_get(list);
 }
 
+static bool skb_frag_is_pp_page(struct page *page)
+{
+	return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
+}
+
 #if IS_ENABLED(CONFIG_PAGE_POOL)
 bool napi_pp_put_page(struct page *page, bool napi_safe)
 {
@@ -905,7 +910,7 @@ bool napi_pp_put_page(struct page *page, bool napi_safe)
 	 * and page_is_pfmemalloc() is checked in __page_pool_put_page()
 	 * to avoid recycling the pfmemalloc page.
 	 */
-	if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
+	if (unlikely(!skb_frag_is_pp_page(page)))
 		return false;
 
 	pp = page->pp;
-- 
2.31.1

Re: [PATCH net-next v6 3/4] skbuff: Add a function to check if a page belongs to page_pool

[Ilias Apalodimas]

The second time is the charm, apologize for the noise.. resending it
as plain-text

On Thu, 30 Nov 2023 at 13:59, Liang Chen <liangchen.linux@gmail.com> wrote:
>
> Wrap code for checking if a page is a page_pool page into a
> function for better readability and ease of reuse.
>
> Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
> Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
> ---
>  net/core/skbuff.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index b157efea5dea..31e57c29c556 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -890,6 +890,11 @@ static void skb_clone_fraglist(struct sk_buff *skb)
>                 skb_get(list);
>  }
>
> +static bool skb_frag_is_pp_page(struct page *page)
> +{
> +       return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
> +}
> +

That's fine, but why _frag? The same logic applies to non-fragmented pages no?
So rename it to skb_from_pp()?

[...]

Thanks
/Ilias

Re: [PATCH net-next v6 3/4] skbuff: Add a function to check if a page belongs to page_pool

[Liang Chen]

On Fri, Dec 1, 2023 at 6:23 PM Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
>
> The second time is the charm, apologize for the noise.. resending it
> as plain-text
>
> On Thu, 30 Nov 2023 at 13:59, Liang Chen <liangchen.linux@gmail.com> wrote:
> >
> > Wrap code for checking if a page is a page_pool page into a
> > function for better readability and ease of reuse.
> >
> > Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
> > Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
> > ---
> >  net/core/skbuff.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index b157efea5dea..31e57c29c556 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -890,6 +890,11 @@ static void skb_clone_fraglist(struct sk_buff *skb)
> >                 skb_get(list);
> >  }
> >
> > +static bool skb_frag_is_pp_page(struct page *page)
> > +{
> > +       return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
> > +}
> > +
>
> That's fine, but why _frag? The same logic applies to non-fragmented pages no?
> So rename it to skb_from_pp()?
>

Yeah, the same logic applies to non-fragmented pages. How about
changing it to 'is_pp_page'? It takes a page as an argument instead of
the entire skb.
> [...]
>
> Thanks
> /Ilias

Re: [PATCH net-next v6 3/4] skbuff: Add a function to check if a page belongs to page_pool

[Ilias Apalodimas]

Hi Liang,

On Mon, 4 Dec 2023 at 04:40, Liang Chen <liangchen.linux@gmail.com> wrote:
>
> On Fri, Dec 1, 2023 at 6:23 PM Ilias Apalodimas
> <ilias.apalodimas@linaro.org> wrote:
> >
> > The second time is the charm, apologize for the noise.. resending it
> > as plain-text
> >
> > On Thu, 30 Nov 2023 at 13:59, Liang Chen <liangchen.linux@gmail.com> wrote:
> > >
> > > Wrap code for checking if a page is a page_pool page into a
> > > function for better readability and ease of reuse.
> > >
> > > Signed-off-by: Liang Chen <liangchen.linux@gmail.com>
> > > Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
> > > ---
> > >  net/core/skbuff.c | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > > index b157efea5dea..31e57c29c556 100644
> > > --- a/net/core/skbuff.c
> > > +++ b/net/core/skbuff.c
> > > @@ -890,6 +890,11 @@ static void skb_clone_fraglist(struct sk_buff *skb)
> > >                 skb_get(list);
> > >  }
> > >
> > > +static bool skb_frag_is_pp_page(struct page *page)
> > > +{
> > > +       return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
> > > +}
> > > +
> >
> > That's fine, but why _frag? The same logic applies to non-fragmented pages no?
> > So rename it to skb_from_pp()?
> >
>
> Yeah, the same logic applies to non-fragmented pages. How about
> changing it to 'is_pp_page'? It takes a page as an argument instead of
> the entire skb.

Naming stuff is always hard. Any of skb_from_pp/is_pp_page would work for me

Thanks
/Ilias
> > [...]
> >
> > Thanks
> > /Ilias

[PATCH net-next v6 4/4] 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>
Reviewed-by: Yunsheng Lin <linyunsheng@huawei.com>
Suggested-by: Jason Wang <jasowang@redhat.com>
---
 include/net/page_pool/helpers.h |  5 ++++
 net/core/skbuff.c               | 41 +++++++++++++++++++++++----------
 2 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 9dc8eaf8a959..268bc9d9ffd3 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -278,6 +278,11 @@ static inline long page_pool_unref_page(struct page *page, long nr)
 	return ret;
 }
 
+static inline void page_pool_ref_page(struct page *page)
+{
+	atomic_long_inc(&page->pp_ref_count);
+}
+
 static inline bool page_pool_is_last_ref(struct page *page)
 {
 	/* If page_pool_unref_page() returns 0, we were the last user */
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 31e57c29c556..2d797f33d809 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -947,6 +947,24 @@ static bool skb_pp_recycle(struct sk_buff *skb, void *data, bool napi_safe)
 	return napi_pp_put_page(virt_to_page(data), napi_safe);
 }
 
+/**
+ * skb_pp_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 void skb_pp_frag_ref(struct page *page)
+{
+	struct page *head_page = compound_head(page);
+
+	if (likely(skb_frag_is_pp_page(head_page)))
+		page_pool_ref_page(head_page);
+	else
+		page_ref_inc(head_page);
+}
+
 static void skb_kfree_head(void *head, unsigned int end_offset)
 {
 	if (end_offset == SKB_SMALL_HEAD_HEADROOM)
@@ -5769,17 +5787,12 @@ 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)) {
@@ -5836,8 +5849,12 @@ 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++)
+			skb_pp_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 v6 4/4] skbuff: Optimization of SKB coalescing for page pool

[Ilias Apalodimas]

HI Liang,

[...]

>  }
>
> +/**
> + * skb_pp_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 void skb_pp_frag_ref(struct page *page)
> +{
> +       struct page *head_page = compound_head(page);
> +
> +       if (likely(skb_frag_is_pp_page(head_page)))
> +               page_pool_ref_page(head_page);
> +       else
> +               page_ref_inc(head_page);

I think I've mentioned this in the past, but I think shoehorning page
pool awareness in the skbuff is not the direction we want to go. Up to
now, we've tried hard to make that as seamless as possible.
The code looks correct, but I'd prefer people with a better
understanding of the core network stack to comment on this.

[...]

Thanks
/Ilias