On Fri, Apr 18, 2025 at 06:34:07PM +0100, Simon Horman wrote: > On Fri, Apr 18, 2025 at 01:00:24AM +0200, [email protected] > wrote: > > From: Ilpo Järvinen <[email protected]> > > > > 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 <[email protected]> > > Co-developed-by: Chia-Yu Chang <[email protected]> > > Signed-off-by: Chia-Yu Chang <[email protected]> > > --- > > 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
