From: David Miller <davem@davemloft.net>
To: pabeni@redhat.com
Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, pjt@google.com,
linux-kernel@vger.kernel.org, ecree@solarflare.com,
dwmw2@infradead.org
Subject: Re: [PATCH net-next v3 0/4] net: mitigate retpoline overhead
Date: Sat, 15 Dec 2018 13:23:33 -0800 (PST) [thread overview]
Message-ID: <20181215.132333.867660599141318055.davem@davemloft.net> (raw)
In-Reply-To: <cover.1544784419.git.pabeni@redhat.com>
From: Paolo Abeni <pabeni@redhat.com>
Date: Fri, 14 Dec 2018 11:51:56 +0100
> 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.
...
Series applied, I'll push this out after a build check completes.
Thanks.
next prev parent reply other threads:[~2018-12-15 21:23 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-14 10:51 [PATCH net-next v3 0/4] net: mitigate retpoline overhead Paolo Abeni
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 ` David Miller [this message]
2018-12-16 18:55 ` [PATCH net-next v3 0/4] net: mitigate retpoline overhead Paolo Abeni
2018-12-16 19:13 ` David Miller
2018-12-16 20:05 ` Willem de Bruijn
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