In [1] & [2] & [3], there are usecases for veth and virtio_net
to use frag support in page pool to reduce memory usage, and it
may request different frag size depending on the head/tail
room space for xdp_frame/shinfo and mtu/packet size. When the
requested frag size is large enough that a single page can not
be split into more than one frag, using frag support only have
performance penalty because of the extra frag count handling
for frag support.

So this patchset provides a page pool API for the driver to
allocate memory with least memory utilization and performance
penalty when it doesn't know the size of memory it need
beforehand.

1. https://patchwork.kernel.org/project/netdevbpf/patch/d3ae6bd3537fbce379382ac6a42f67e22f27ece2.1683896626.git.lorenzo@kernel.org/
2. https://patchwork.kernel.org/project/netdevbpf/patch/20230526054621.18371-3-liangchen.linux@gmail.com/
3. https://github.com/alobakin/linux/tree/iavf-pp-frag

v5 RFC: add a new page_pool_cache_alloc() API, and other minor
        change as discussed in v4. As there seems to be three
        comsumers that might be made use of the new API, so
        repost it as RFC and CC the relevant authors to see
        if the new API fits their need.

V4. Fix a typo and add a patch to update document about frag
    API, PAGE_POOL_DMA_USE_PP_FRAG_COUNT is not renamed yet
    as we may need a different thread to discuss that.

V3: Incorporate changes from the disscusion with Alexander,
    mostly the inline wraper, PAGE_POOL_DMA_USE_PP_FRAG_COUNT
    change split to separate patch and comment change.
V2: Add patch to remove PP_FLAG_PAGE_FRAG flags and mention
    virtio_net usecase in the cover letter.
V1: Drop RFC tag and page_pool_frag patch.

Yunsheng Lin (6):
  page_pool: frag API support for 32-bit arch with 64-bit DMA
  page_pool: unify frag_count handling in page_pool_is_last_frag()
  page_pool: introduce page_pool[_cache]_alloc() API
  page_pool: remove PP_FLAG_PAGE_FRAG flag
  page_pool: update document about frag API
  net: veth: use newly added page pool API for veth with xdp

 Documentation/networking/page_pool.rst        |  34 +++-
 .../net/ethernet/hisilicon/hns3/hns3_enet.c   |   3 +-
 .../marvell/octeontx2/nic/otx2_common.c       |   2 +-
 .../net/ethernet/mellanox/mlx5/core/en_main.c |  12 +-
 drivers/net/veth.c                            |  24 ++-
 drivers/net/wireless/mediatek/mt76/mac80211.c |   2 +-
 include/net/page_pool.h                       | 179 ++++++++++++++----
 net/core/page_pool.c                          |  30 ++-
 net/core/skbuff.c                             |   2 +-
 9 files changed, 212 insertions(+), 76 deletions(-)

-- 
2.33.0

From: Yunsheng Lin <linyunsheng@huawei.com>
Date: Thu, 29 Jun 2023 20:02:20 +0800

> In [1] & [2] & [3], there are usecases for veth and virtio_net
> to use frag support in page pool to reduce memory usage, and it
> may request different frag size depending on the head/tail
> room space for xdp_frame/shinfo and mtu/packet size. When the
> requested frag size is large enough that a single page can not
> be split into more than one frag, using frag support only have
> performance penalty because of the extra frag count handling
> for frag support.
> 
> So this patchset provides a page pool API for the driver to
> allocate memory with least memory utilization and performance
> penalty when it doesn't know the size of memory it need
> beforehand.
> 
> 1. https://patchwork.kernel.org/project/netdevbpf/patch/d3ae6bd3537fbce379382ac6a42f67e22f27ece2.1683896626.git.lorenzo@kernel.org/
> 2. https://patchwork.kernel.org/project/netdevbpf/patch/20230526054621.18371-3-liangchen.linux@gmail.com/
> 3. https://github.com/alobakin/linux/tree/iavf-pp-frag

Thanks for sharing the link :D

> 
> v5 RFC: add a new page_pool_cache_alloc() API, and other minor
>         change as discussed in v4. As there seems to be three
>         comsumers that might be made use of the new API, so
>         repost it as RFC and CC the relevant authors to see
>         if the new API fits their need.

Tested v5 against my latest tree, no regressions, perf is even a bit
better than it was. That also might've come from that net-next pulled
Linus' tree with a good bunch of PRs already merged, or from v4 -> v5
update.

Re consumers, I'm planning to send the RFC series with IAVF as a
consumer on Monday (and a couple generic Page Pool improvements today,
will see).

> 
> V4. Fix a typo and add a patch to update document about frag
>     API, PAGE_POOL_DMA_USE_PP_FRAG_COUNT is not renamed yet
>     as we may need a different thread to discuss that.
> 
> V3: Incorporate changes from the disscusion with Alexander,
>     mostly the inline wraper, PAGE_POOL_DMA_USE_PP_FRAG_COUNT
>     change split to separate patch and comment change.
> V2: Add patch to remove PP_FLAG_PAGE_FRAG flags and mention
>     virtio_net usecase in the cover letter.
> V1: Drop RFC tag and page_pool_frag patch.
Thanks,
Olek

On 2023/6/29 22:26, Alexander Lobakin wrote:
>> v5 RFC: add a new page_pool_cache_alloc() API, and other minor
>>         change as discussed in v4. As there seems to be three
>>         comsumers that might be made use of the new API, so
>>         repost it as RFC and CC the relevant authors to see
>>         if the new API fits their need.
> 
> Tested v5 against my latest tree, no regressions, perf is even a bit
> better than it was. That also might've come from that net-next pulled
> Linus' tree with a good bunch of PRs already merged, or from v4 -> v5
> update.

v4 -> v5 is mostly about adding the page pool cache API, so I believe the
perf improvement is from the net-next pull:)

> 
> Re consumers, I'm planning to send the RFC series with IAVF as a
> consumer on Monday (and a couple generic Page Pool improvements today,
> will see).

Thanks.