On Wed, 19 Feb 2025 09:28:09 +0100 Greg Kroah-Hartman wrote:
> 6.13-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Paolo Abeni <pabeni@xxxxxxxxxx>
>
> [ Upstream commit 011b0335903832facca86cd8ed05d7d8d94c9c76 ]
>
> This reverts commit dbae2b062824 ("net: skb: introduce and use a single
> page frag cache"). The intended goal of such change was to counter a
> performance regression introduced by commit 3226b158e67c ("net: avoid
> 32 x truesize under-estimation for tiny skbs").
>
> Unfortunately, the blamed commit introduces another regression for the
> virtio_net driver. Such a driver calls napi_alloc_skb() with a tiny
> size, so that the whole head frag could fit a 512-byte block.
>
> The single page frag cache uses a 1K fragment for such allocation, and
> the additional overhead, under small UDP packets flood, makes the page
> allocator a bottleneck.
>
> Thanks to commit bf9f1baa279f ("net: add dedicated kmem_cache for
> typical/small skb->head"), this revert does not re-introduce the
> original regression. Actually, in the relevant test on top of this
> revert, I measure a small but noticeable positive delta, just above
> noise level.
>
> The revert itself required some additional mangling due to the
> introduction of the SKB_HEAD_ALIGN() helper and local lock infra in the
> affected code.
>
> Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> Fixes: dbae2b062824 ("net: skb: introduce and use a single page frag cache")
> Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
> Link: https://patch.msgid.link/e649212fde9f0fdee23909ca0d14158d32bb7425.1738877290.git.pabeni@xxxxxxxxxx
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
As already pointed out this was reverted
