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Date: Tue, 14 May 2024 07:14:07 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Richard Gobert <richardbgobert@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>, davem@davemloft.net,
 edumazet@google.com, pabeni@redhat.com, willemdebruijn.kernel@gmail.com,
 dsahern@kernel.org, alexander.duyck@gmail.com, shuah@kernel.org,
 netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
 linux-kselftest@vger.kernel.org
Subject: Re: [PATCH net-next v10 2/3] net: gro: move L3 flush checks to
 tcp_gro_receive and udp_gro_receive_segment
Message-ID: <20240514071407.257c0003@kernel.org>
In-Reply-To: <CAMuHMdXFJwxexojG+41ppD=2EmyXsVM6bwh+-cxCxfSsM_yJiw@mail.gmail.com>
References: <20240509190819.2985-1-richardbgobert@gmail.com>
	<20240509190819.2985-3-richardbgobert@gmail.com>
	<CAMuHMdXFJwxexojG+41ppD=2EmyXsVM6bwh+-cxCxfSsM_yJiw@mail.gmail.com>
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On Tue, 14 May 2024 14:13:21 +0200 Geert Uytterhoeven wrote:
> On Thu, May 9, 2024 at 9:09=E2=80=AFPM Richard Gobert <richardbgobert@gma=
il.com> wrote:
> > {inet,ipv6}_gro_receive functions perform flush checks (ttl, flags,
> > iph->id, ...) against all packets in a loop. These flush checks are use=
d in
> > all merging UDP and TCP flows.
> >
> > These checks need to be done only once and only against the found p skb,
> > since they only affect flush and not same_flow.
> >
> > This patch leverages correct network header offsets from the cb for both
> > outer and inner network headers - allowing these checks to be done only
> > once, in tcp_gro_receive and udp_gro_receive_segment. As a result,
> > NAPI_GRO_CB(p)->flush is not used at all. In addition, flush_id checks =
are
> > more declarative and contained in inet_gro_flush, thus removing the need
> > for flush_id in napi_gro_cb.
> >
> > This results in less parsing code for non-loop flush tests for TCP and =
UDP
> > flows.
> >
> > To make sure results are not within noise range - I've made netfilter d=
rop
> > all TCP packets, and measured CPU performance in GRO (in this case GRO =
is
> > responsible for about 50% of the CPU utilization).
> >
> > perf top while replaying 64 parallel IP/TCP streams merging in GRO:
> > (gro_receive_network_flush is compiled inline to tcp_gro_receive)
> > net-next:
> >         6.94% [kernel] [k] inet_gro_receive
> >         3.02% [kernel] [k] tcp_gro_receive
> >
> > patch applied:
> >         4.27% [kernel] [k] tcp_gro_receive
> >         4.22% [kernel] [k] inet_gro_receive
> >
> > perf top while replaying 64 parallel IP/IP/TCP streams merging in GRO (=
same
> > results for any encapsulation, in this case inet_gro_receive is top
> > offender in net-next)
> > net-next:
> >         10.09% [kernel] [k] inet_gro_receive
> >         2.08% [kernel] [k] tcp_gro_receive
> >
> > patch applied:
> >         6.97% [kernel] [k] inet_gro_receive
> >         3.68% [kernel] [k] tcp_gro_receive
> >
> > Signed-off-by: Richard Gobert <richardbgobert@gmail.com> =20
>=20
> Thanks for your patch, which is now commit 4b0ebbca3e167976 ("net: gro:
> move L3 flush checks to tcp_gro_receive and udp_gro_receive_segment")
> in net-next/main (next-20240514).
>=20
> noreply@ellerman.id.au reports build failures on m68k, e.g.
> http://kisskb.ellerman.id.au/kisskb/buildresult/15168903/
>=20
>     net/core/gro.c: In function =E2=80=98dev_gro_receive=E2=80=99:
>     ././include/linux/compiler_types.h:460:38: error: call to
> =E2=80=98__compiletime_assert_654=E2=80=99 declared with attribute error:=
 BUILD_BUG_ON
> failed: !IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed), sizeof(u32))

Hi Richard, any chance of getting this fixed within the next 2 hours?
I can't send the net-next PR if it doesn't build on one of the arches..