From: Alexander Duyck <alexander.duyck@gmail.com>
To: Paolo Abeni <pabeni@redhat.com>
Cc: Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Yunsheng Lin <linyunsheng@huawei.com>,
nbd@nbd.name, davem@davemloft.net, hawk@kernel.org,
ilias.apalodimas@linaro.org, linux-kernel@vger.kernel.org,
lorenzo@kernel.org, netdev@vger.kernel.org
Subject: Re: [net PATCH] skb: Do mix page pool and page referenced frags in GRO
Date: Mon, 30 Jan 2023 08:17:58 -0800 [thread overview]
Message-ID: <CAKgT0UcwrQ21F2mgaLK2ruWUsRbiuSd=T=V=e1P4GUpAfbxPgQ@mail.gmail.com> (raw)
In-Reply-To: <ec534eacabf5c859930eb5ca7f417f7f01197d24.camel@redhat.com>
On Mon, Jan 30, 2023 at 12:50 AM Paolo Abeni <pabeni@redhat.com> wrote:
>
> On Sat, 2023-01-28 at 08:08 +0100, Eric Dumazet wrote:
> > On Sat, Jan 28, 2023 at 6:26 AM Jakub Kicinski <kuba@kernel.org> wrote:
> > >
> > > On Sat, 28 Jan 2023 10:37:47 +0800 Yunsheng Lin wrote:
> > > > If we are not allowing gro for the above case, setting NAPI_GRO_CB(p)->flush
> > > > to 1 in gro_list_prepare() seems to be making more sense so that the above
> > > > case has the same handling as skb_has_frag_list() handling?
> > > > https://elixir.bootlin.com/linux/v6.2-rc4/source/net/core/gro.c#L503
> > > >
> > > > As it seems to avoid some unnecessary operation according to comment
> > > > in tcp4_gro_receive():
> > > > https://elixir.bootlin.com/linux/v6.2-rc4/source/net/ipv4/tcp_offload.c#L322
> > >
> > > The frag_list case can be determined with just the input skb.
> > > For pp_recycle we need to compare input skb's pp_recycle with
> > > the pp_recycle of the skb already held by GRO.
> > >
> > > I'll hold off with applying a bit longer tho, in case Eric
> > > wants to chime in with an ack or opinion.
> >
> > We can say that we are adding in the fast path an expensive check
> > about an unlikely condition.
> >
> > GRO is by far the most expensive component in our stack.
>
> Slightly related to the above: currently the GRO engine performs the
> skb metadata check for every packet. My understanding is that even with
> XDP enabled and ebpf running on the given packet, the skb should
> usually have meta_len == 0.
>
> What about setting 'skb->slow_gro' together with meta_len and moving
> the skb_metadata_differs() check under the slow_gro guard?
Makes sense to me, especially since we have to do a pointer chase to
get the metadata length out of the shared info.
Looking at the code one thing I was wondering about is if we should be
flagging frames where one is slow_gro and one is not as having a diff
and just skipping the checks since we know the slow_gro checks are
expensive and if they differ based on that flag odds are one will have
a field present that the other doesn't.
next prev parent reply other threads:[~2023-01-30 16:18 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-24 12:43 [PATCH] net: page_pool: fix refcounting issues with fragmented allocation Felix Fietkau
2023-01-24 14:11 ` Ilias Apalodimas
2023-01-24 15:57 ` Alexander H Duyck
2023-01-24 16:59 ` Felix Fietkau
2023-01-26 10:31 ` Ilias Apalodimas
2023-01-26 15:41 ` Alexander Duyck
2023-01-26 16:05 ` Ilias Apalodimas
2023-01-24 17:22 ` Felix Fietkau
2023-01-24 21:10 ` Alexander H Duyck
2023-01-24 21:30 ` Felix Fietkau
2023-01-25 17:11 ` Alexander H Duyck
2023-01-25 17:32 ` Felix Fietkau
2023-01-25 18:26 ` Alexander H Duyck
2023-01-25 18:42 ` Felix Fietkau
2023-01-25 19:02 ` Alexander H Duyck
2023-01-25 19:10 ` Felix Fietkau
2023-01-25 19:40 ` Felix Fietkau
2023-01-25 20:02 ` Felix Fietkau
2023-01-25 22:14 ` Alexander H Duyck
2023-01-26 6:12 ` Felix Fietkau
2023-01-26 9:14 ` Felix Fietkau
2023-01-26 16:08 ` Alexander Duyck
2023-01-26 16:40 ` Alexander Duyck
2023-01-26 17:44 ` Felix Fietkau
2023-01-26 18:38 ` Alexander H Duyck
2023-01-26 18:43 ` Felix Fietkau
2023-01-26 19:06 ` [net PATCH] skb: Do mix page pool and page referenced frags in GRO Alexander Duyck
2023-01-26 19:14 ` Toke Høiland-Jørgensen
2023-01-26 19:48 ` Alexander Duyck
2023-01-26 21:35 ` Toke Høiland-Jørgensen
2023-01-26 23:13 ` Jakub Kicinski
2023-01-27 7:15 ` Ilias Apalodimas
2023-01-27 7:21 ` Felix Fietkau
2023-01-30 16:49 ` Jesper Dangaard Brouer
2023-01-28 2:37 ` Yunsheng Lin
2023-01-28 5:26 ` Jakub Kicinski
2023-01-28 7:08 ` Eric Dumazet
2023-01-30 8:50 ` Paolo Abeni
2023-01-30 16:17 ` Alexander Duyck [this message]
2023-01-28 7:15 ` Eric Dumazet
2023-01-28 17:08 ` Alexander Duyck
2023-01-28 7:50 ` patchwork-bot+netdevbpf
2023-01-26 10:32 ` [PATCH] net: page_pool: fix refcounting issues with fragmented allocation Ilias Apalodimas
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