From: Paolo Abeni <pabeni@redhat•com>
To: netdev@vger•kernel.org
Cc: "David S. Miller" <davem@davemloft•net>,
Eric Dumazet <eric.dumazet@gmail•com>
Subject: [PATCH net-next 0/4] net: mitigate retpoline overhead
Date: Mon, 3 Dec 2018 12:40:20 +0100 [thread overview]
Message-ID: <cover.1543836966.git.pabeni@redhat.com> (raw)
The spectre v2 counter-measures, aka retpolines, are a source of measurable
overhead[1]. We can partially address that when the function pointer refers to
a builtin symbol resorting to a list of tests vs well-known builtin function and
direct calls.
Experimental results[2] shows that replacing a single indirect calls via
retpoline with several branches and direct calls gives performance gains
even when multiple branches are added - 5 or more, as reported in [2].
This may lead to some uglification around the indirect calls. In netconf 2018
Eric Dumazet described a technique to hide the most relevant part of the needed
boilerplate with some macro help.
This series is a [re-]implementation of such idea, exposing the introduced
helpers in a new header file. They are later leveraged to avoid the indirect
call overhead in the GRO path, when possible.
Overall this gives > 10% performance improvement for UDP GRO benchmark, and
smaller but measurable for TCP syn flood.
The added infra can be used in follow-up patches to cope with retpoline overhead
in other points of the networking stack (e.g. at the qdisc layer) and possibly
even in other subsystems.
rfc -> v1:
- use branch prediction hints, as suggested by Eric
[1] http://vger.kernel.org/netconf2018_files/PaoloAbeni_netconf2018.pdf
[2] https://linuxplumbersconf.org/event/2/contributions/99/attachments/98/117/lpc18_paper_af_xdp_perf-v2.pdf
Paolo Abeni (4):
indirect call wrappers: helpers to speed-up indirect calls of builtin
net: use indirect call wrappers at GRO network layer
net: use indirect call wrapper at GRO transport layer
udp: use indirect call wrapper for GRO socket lookup
include/linux/indirect_call_wrapper.h | 77 +++++++++++++++++++++++++++
include/net/inet_common.h | 9 ++++
net/core/dev.c | 10 +++-
net/ipv4/af_inet.c | 15 +++++-
net/ipv4/tcp_offload.c | 5 ++
net/ipv4/udp.c | 2 +
net/ipv4/udp_offload.c | 11 +++-
net/ipv6/ip6_offload.c | 14 ++++-
net/ipv6/tcpv6_offload.c | 5 ++
net/ipv6/udp.c | 2 +
net/ipv6/udp_offload.c | 5 ++
11 files changed, 147 insertions(+), 8 deletions(-)
create mode 100644 include/linux/indirect_call_wrapper.h
--
2.19.2
next reply other threads:[~2018-12-03 11:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-03 11:40 Paolo Abeni [this message]
2018-12-03 11:40 ` [PATCH net-next 1/4] indirect call wrappers: helpers to speed-up indirect calls of builtin Paolo Abeni
2018-12-03 18:04 ` Eric Dumazet
2018-12-04 11:27 ` Paolo Abeni
2018-12-04 16:51 ` David Miller
2018-12-04 17:13 ` Edward Cree
2018-12-04 17:44 ` Paolo Abeni
2018-12-04 18:12 ` Edward Cree
2018-12-05 18:03 ` Paolo Abeni
2018-12-03 11:40 ` [PATCH net-next 2/4] net: use indirect call wrappers at GRO network layer Paolo Abeni
2018-12-03 11:40 ` [PATCH net-next 3/4] net: use indirect call wrapper at GRO transport layer Paolo Abeni
2018-12-07 3:48 ` kbuild test robot
2018-12-03 11:40 ` [PATCH net-next 4/4] udp: use indirect call wrapper for GRO socket lookup Paolo Abeni
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cover.1543836966.git.pabeni@redhat.com \
--to=pabeni@redhat$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox