From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8FAB6433C4; Fri, 18 Apr 2025 18:25:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745000706; cv=none; b=cOYAC4W5tBuDUxRYXiPMX9COrbW7ROW3jOiJoQ5LurPA7TCDLhfMBHYBol4QSoO88mIDvl14PpHghAMB8CMtTjNJPcdbL9qACwb9ZbIEGsSX3Z4S7vQx7dpOv5+DkWVe0QsN+shBAYE0ctghr3qY0BAabXHMOV7BNnHyL32FKXM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745000706; c=relaxed/simple; bh=zNvM+9e+tIM6UJOBfEekJ+HovdNbvDGHEioljB6B4SE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=lTEW7paY1JqKPjqWpCTB51472I+b66ww4/bgPb0tNOCjqPkWaMe5B6V8tQlN+zKzlB6SjMiYdI/ThKlRICvUUggAo1Q9mFTRfLpo80hD3znDOfa87TNPO1KWLomWIPPBtn9E4Tv3jG3ZkSBKGX2KZ/txQUPoo5NRCN1BHpemdg0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KENOMtLP; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KENOMtLP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A94B3C4CEE2; Fri, 18 Apr 2025 18:25:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745000705; bh=zNvM+9e+tIM6UJOBfEekJ+HovdNbvDGHEioljB6B4SE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KENOMtLP1ihb4f3t2ihSsb2p4rz6JxOuYcEe44ElmXksWSB/0dTvKHHYsdz+SEfoY Jjqoj/wse8Pt+tnjJ6/RDrwQdSJ2VfD5DEK45Mw/tTKoJho3HCkVuhiYcUtCanFoiG cRZadhLlhyT8bYaZnKyleRWOJbIhIxd1yDS3Oq0oMWp/8abuFEUaZoXzQtHzCKQ4Zv S5VEZnczDGe9p8iOOh9bSrQAbxJIfv/ruq+v7+ZZYBS/StfbXQi5gQr4n82Jcv5pji hCozGfPX9MUPhlum+RuX3mJ4tAIjjNnhSAq+6riUbuKnz0qpt67pjDF+bKnCkTY/BH e4zFByJggvmrg== Date: Fri, 18 Apr 2025 19:24:58 +0100 From: Simon Horman To: chia-yu.chang@nokia-bell-labs.com Cc: dsahern@kernel.org, kuniyu@amazon.com, bpf@vger.kernel.org, netdev@vger.kernel.org, dave.taht@gmail.com, pabeni@redhat.com, jhs@mojatatu.com, kuba@kernel.org, stephen@networkplumber.org, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, edumazet@google.com, andrew+netdev@lunn.ch, donald.hunter@gmail.com, ast@fiberby.net, liuhangbin@gmail.com, shuah@kernel.org, linux-kselftest@vger.kernel.org, ij@kernel.org, ncardwell@google.com, koen.de_schepper@nokia-bell-labs.com, g.white@cablelabs.com, ingemar.s.johansson@ericsson.com, mirja.kuehlewind@ericsson.com, cheshire@apple.com, rs.ietf@gmx.at, Jason_Livingood@comcast.com, vidhi_goel@apple.com Subject: Re: [PATCH v4 net-next 10/15] tcp: accecn: AccECN option send control Message-ID: <20250418182458.GD2676982@horms.kernel.org> References: <20250417230029.21905-1-chia-yu.chang@nokia-bell-labs.com> <20250417230029.21905-11-chia-yu.chang@nokia-bell-labs.com> <20250418173407.GC2676982@horms.kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250418173407.GC2676982@horms.kernel.org> On Fri, Apr 18, 2025 at 06:34:07PM +0100, Simon Horman wrote: > On Fri, Apr 18, 2025 at 01:00:24AM +0200, chia-yu.chang@nokia-bell-labs.com wrote: > > From: Ilpo Järvinen > > > > Instead of sending the option in every ACK, limit sending to > > those ACKs where the option is necessary: > > - Handshake > > - "Change-triggered ACK" + the ACK following it. The > > 2nd ACK is necessary to unambiguously indicate which > > of the ECN byte counters in increasing. The first > > ACK has two counters increasing due to the ecnfield > > edge. > > - ACKs with CE to allow CEP delta validations to take > > advantage of the option. > > - Force option to be sent every at least once per 2^22 > > bytes. The check is done using the bit edges of the > > byte counters (avoids need for extra variables). > > - AccECN option beacon to send a few times per RTT even if > > nothing in the ECN state requires that. The default is 3 > > times per RTT, and its period can be set via > > sysctl_tcp_ecn_option_beacon. > > > > Signed-off-by: Ilpo Järvinen > > Co-developed-by: Chia-Yu Chang > > Signed-off-by: Chia-Yu Chang > > --- > > include/linux/tcp.h | 3 +++ > > include/net/netns/ipv4.h | 1 + > > include/net/tcp.h | 1 + > > net/ipv4/sysctl_net_ipv4.c | 9 ++++++++ > > net/ipv4/tcp.c | 5 ++++- > > net/ipv4/tcp_input.c | 36 +++++++++++++++++++++++++++++++- > > net/ipv4/tcp_ipv4.c | 1 + > > net/ipv4/tcp_minisocks.c | 2 ++ > > net/ipv4/tcp_output.c | 42 ++++++++++++++++++++++++++++++-------- > > 9 files changed, 90 insertions(+), 10 deletions(-) > > > > diff --git a/include/linux/tcp.h b/include/linux/tcp.h > > index 0e032d9631ac..9619524d8901 100644 > > --- a/include/linux/tcp.h > > +++ b/include/linux/tcp.h > > @@ -309,7 +309,10 @@ struct tcp_sock { > > u8 received_ce_pending:4, /* Not yet transmit cnt of received_ce */ > > unused2:4; > > u8 accecn_minlen:2,/* Minimum length of AccECN option sent */ > > + prev_ecnfield:2,/* ECN bits from the previous segment */ > > + accecn_opt_demand:2,/* Demand AccECN option for n next ACKs */ > > est_ecnfield:2;/* ECN field for AccECN delivered estimates */ > > + u64 accecn_opt_tstamp; /* Last AccECN option sent timestamp */ > > u32 app_limited; /* limited until "delivered" reaches this val */ > > u32 rcv_wnd; /* Current receiver window */ > > /* > > ... > > > @@ -5113,7 +5116,7 @@ static void __init tcp_struct_check(void) > > /* 32bit arches with 8byte alignment on u64 fields might need padding > > * before tcp_clock_cache. > > */ > > - CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_txrx, 122 + 6); > > + CACHELINE_ASSERT_GROUP_SIZE(struct tcp_sock, tcp_sock_write_txrx, 130 + 6); > > Hi, > > While this seems find on x86_64, x86_32 and arm64, it does not seem correct > on ARM (32-bit). > > This is because the existing two byte hole after est_ecnfield grows > to 6 bytes. I assume this is because of alignment requirements. > But in any case, the result is that the overall group size increases > by 12 bytes rather than 8. > > I believe that you can avoid the hole growing, and thus limit the overall > increase in size of the group to 12 bytes, by placing accecn_opt_tstamp > elsewhere, e.g. after app_limited rather than before it. > > You can exercise this by cross compiling for ARM and examining > the structure layout using pahole. > > Cross compilers available from [1] should be able to do that something > like this: > > PATH=".../gcc-14.2.0-nolibc/arm-linux-gnueabi/bin:$PATH" > export ARCH=arm > export CROSS_COMPILE=arm-linux-gnueabi- > > make allmodconfig > echo "CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y" >> .config > yes "" | make oldconfig > > make net/ipv4/tcp.o Sorry, I omitted the invocation of pahole. pahole net/ipv4/tcp.o > [1] https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/14.2.0/ -- pw-bot: changes-requested