From: Paolo Abeni <pabeni@redhat.com>
To: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <eric.dumazet@gmail.com>,
Paul Turner <pjt@google.com>,
linux-kernel@vger.kernel.org, Edward Cree <ecree@solarflare.com>,
David Woodhouse <dwmw2@infradead.org>
Subject: [PATCH net-next v3 0/4] net: mitigate retpoline overhead
Date: Fri, 14 Dec 2018 11:51:56 +0100 [thread overview]
Message-ID: <cover.1544784419.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 show that replacing a single indirect call via
retpoline with several branches and a direct call 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.
v2 -> v3:
- fix build error with CONFIG_IPV6=m
v1 -> v2:
- list explicitly the builtin function names in INDIRECT_CALL_*(),
as suggested by Ed Cree
- expand the recipients list
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 wrappers at GRO transport layer
udp: use indirect call wrappers for GRO socket lookup
include/linux/indirect_call_wrapper.h | 51 +++++++++++++++++++++++++++
include/net/inet_common.h | 9 +++++
net/core/dev.c | 15 ++++++--
net/ipv4/af_inet.c | 13 +++++--
net/ipv4/tcp_offload.c | 6 ++--
net/ipv4/udp_offload.c | 15 +++++---
net/ipv6/ip6_offload.c | 35 +++++++++++++++---
net/ipv6/tcpv6_offload.c | 7 ++--
net/ipv6/udp_offload.c | 7 ++--
9 files changed, 136 insertions(+), 22 deletions(-)
create mode 100644 include/linux/indirect_call_wrapper.h
--
2.19.2
next reply other threads:[~2018-12-14 10:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-14 10:51 Paolo Abeni [this message]
2018-12-14 10:51 ` [PATCH net-next v3 1/4] indirect call wrappers: helpers to speed-up indirect calls of builtin Paolo Abeni
2018-12-14 10:51 ` [PATCH net-next v3 2/4] net: use indirect call wrappers at GRO network layer Paolo Abeni
2018-12-14 10:51 ` [PATCH net-next v3 3/4] net: use indirect call wrappers at GRO transport layer Paolo Abeni
2018-12-14 10:52 ` [PATCH net-next v3 4/4] udp: use indirect call wrappers for GRO socket lookup Paolo Abeni
2018-12-15 21:23 ` [PATCH net-next v3 0/4] net: mitigate retpoline overhead David Miller
2018-12-16 18:55 ` Paolo Abeni
2018-12-16 19:13 ` David Miller
2018-12-16 20:05 ` Willem de Bruijn
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.1544784419.git.pabeni@redhat.com \
--to=pabeni@redhat.com \
--cc=davem@davemloft.net \
--cc=dwmw2@infradead.org \
--cc=ecree@solarflare.com \
--cc=eric.dumazet@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=pjt@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).