| Message ID | 20231212044614.42733-5-liangchen.linux@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | skbuff: Optimize SKB coalescing for page pool | expand |
On Mon, Dec 11, 2023 at 8:47 PM Liang Chen <liangchen.linux@gmail.com> wrote: > > 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 | 43 ++++++++++++++++++++++++--------- > 2 files changed, 36 insertions(+), 12 deletions(-) > > diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h > index d0c5e7e6857a..0dc8fab43bef 100644 > --- a/include/net/page_pool/helpers.h > +++ b/include/net/page_pool/helpers.h > @@ -281,6 +281,11 @@ 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 7e26b56cda38..783a04733109 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -947,6 +947,26 @@ 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 the fragment reference count (pp_ref_count) of a page. This is > + * intended to gain a fragment reference only for page pool aware skbs, > + * i.e. when skb->pp_recycle is true, and not for fragments in a > + * non-pp-recycling skb. It has a fallback to increase a reference on a > + * normal page, as page pool aware skbs may also have normal page fragments. > + */ > +static void skb_pp_frag_ref(struct page *page) > +{ > + struct page *head_page = compound_head(page); > + Feel free to not delay this patch series further based on this comment/question, but... I'm a bit confused about the need for compound_head() here, but skb_frag_ref() doesn't first obtain the compound_head(). Is there a page_pool specific reason why skb_frag_ref() can get_page() directly but this helper needs to grab the compound_head() first? > + if (likely(is_pp_page(head_page))) > + page_pool_ref_page(head_page); > + else > + page_ref_inc(head_page); Any reason why not get_page() here? > +} > + > static void skb_kfree_head(void *head, unsigned int end_offset) > { > if (end_offset == SKB_SMALL_HEAD_HEADROOM) > @@ -5769,17 +5789,12 @@ 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 +5851,12 @@ 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 >
On Wed, Dec 13, 2023 at 9:49 AM Mina Almasry <almasrymina@google.com> wrote: > > On Mon, Dec 11, 2023 at 8:47 PM Liang Chen <liangchen.linux@gmail.com> wrote: > > > > 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 | 43 ++++++++++++++++++++++++--------- > > 2 files changed, 36 insertions(+), 12 deletions(-) > > > > diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h > > index d0c5e7e6857a..0dc8fab43bef 100644 > > --- a/include/net/page_pool/helpers.h > > +++ b/include/net/page_pool/helpers.h > > @@ -281,6 +281,11 @@ 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 7e26b56cda38..783a04733109 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -947,6 +947,26 @@ 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 the fragment reference count (pp_ref_count) of a page. This is > > + * intended to gain a fragment reference only for page pool aware skbs, > > + * i.e. when skb->pp_recycle is true, and not for fragments in a > > + * non-pp-recycling skb. It has a fallback to increase a reference on a > > + * normal page, as page pool aware skbs may also have normal page fragments. > > + */ > > +static void skb_pp_frag_ref(struct page *page) > > +{ > > + struct page *head_page = compound_head(page); > > + > > Feel free to not delay this patch series further based on this > comment/question, but... > > I'm a bit confused about the need for compound_head() here, but > skb_frag_ref() doesn't first obtain the compound_head(). Is there a > page_pool specific reason why skb_frag_ref() can get_page() directly > but this helper needs to grab the compound_head() first? > get_page includes the call to compound_head, so skb_frag_ref indirectly calls compound_head as well. > > + if (likely(is_pp_page(head_page))) > > + page_pool_ref_page(head_page); > > + else > > + page_ref_inc(head_page); > > Any reason why not get_page() here? > head_page is a head page because of the compound_head call above. This was actually a comment received from a previous iteration:) > > +} > > + > > static void skb_kfree_head(void *head, unsigned int end_offset) > > { > > if (end_offset == SKB_SMALL_HEAD_HEADROOM) > > @@ -5769,17 +5789,12 @@ 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 +5851,12 @@ 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 > > > > > -- > Thanks, > Mina
On Tue, Dec 12, 2023 at 6:37 PM Liang Chen <liangchen.linux@gmail.com> wrote: > > On Wed, Dec 13, 2023 at 9:49 AM Mina Almasry <almasrymina@google.com> wrote: > > > > On Mon, Dec 11, 2023 at 8:47 PM Liang Chen <liangchen.linux@gmail.com> wrote: > > > > > > 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 | 43 ++++++++++++++++++++++++--------- > > > 2 files changed, 36 insertions(+), 12 deletions(-) > > > > > > diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h > > > index d0c5e7e6857a..0dc8fab43bef 100644 > > > --- a/include/net/page_pool/helpers.h > > > +++ b/include/net/page_pool/helpers.h > > > @@ -281,6 +281,11 @@ 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 7e26b56cda38..783a04733109 100644 > > > --- a/net/core/skbuff.c > > > +++ b/net/core/skbuff.c > > > @@ -947,6 +947,26 @@ 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 the fragment reference count (pp_ref_count) of a page. This is > > > + * intended to gain a fragment reference only for page pool aware skbs, > > > + * i.e. when skb->pp_recycle is true, and not for fragments in a > > > + * non-pp-recycling skb. It has a fallback to increase a reference on a > > > + * normal page, as page pool aware skbs may also have normal page fragments. > > > + */ > > > +static void skb_pp_frag_ref(struct page *page) > > > +{ > > > + struct page *head_page = compound_head(page); > > > + > > > > Feel free to not delay this patch series further based on this > > comment/question, but... > > > > I'm a bit confused about the need for compound_head() here, but > > skb_frag_ref() doesn't first obtain the compound_head(). Is there a > > page_pool specific reason why skb_frag_ref() can get_page() directly > > but this helper needs to grab the compound_head() first? > > > > get_page includes the call to compound_head, so skb_frag_ref > indirectly calls compound_head as well. > > > > + if (likely(is_pp_page(head_page))) > > > + page_pool_ref_page(head_page); > > > + else > > > + page_ref_inc(head_page); > > > > Any reason why not get_page() here? > > > > head_page is a head page because of the compound_head call above. This > was actually a comment received from a previous iteration:) > I see, thanks. Reviewed-by: Mina Almasry <almasrymina@google.com> Noob question: do we actually support someone passing a compound_page to skb_frag_fill_page_desc()? Anyone know of any driver that does this? I kinda like the direction this patch was going instead: https://patchwork.kernel.org/project/netdevbpf/patch/20231113130041.58124-5-linyunsheng@huawei.com/ Where we explicitly exclude compound pages from skbs... This is for convenience for devmem TCP, where I don't support compound pages, but that is more my problem than yours. This patch is fine. > > > +} > > > + > > > static void skb_kfree_head(void *head, unsigned int end_offset) > > > { > > > if (end_offset == SKB_SMALL_HEAD_HEADROOM) > > > @@ -5769,17 +5789,12 @@ 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 +5851,12 @@ 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 > > > > > > > > > -- > > Thanks, > > Mina
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h index d0c5e7e6857a..0dc8fab43bef 100644 --- a/include/net/page_pool/helpers.h +++ b/include/net/page_pool/helpers.h @@ -281,6 +281,11 @@ 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 7e26b56cda38..783a04733109 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -947,6 +947,26 @@ 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 the fragment reference count (pp_ref_count) of a page. This is + * intended to gain a fragment reference only for page pool aware skbs, + * i.e. when skb->pp_recycle is true, and not for fragments in a + * non-pp-recycling skb. It has a fallback to increase a reference on a + * normal page, as page pool aware skbs may also have normal page fragments. + */ +static void skb_pp_frag_ref(struct page *page) +{ + struct page *head_page = compound_head(page); + + if (likely(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 +5789,12 @@ 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 +5851,12 @@ 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;
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 | 43 ++++++++++++++++++++++++--------- 2 files changed, 36 insertions(+), 12 deletions(-)