linux-kernel - Re: [RFC PATCH v2] bridge: make it possible for packets to traverse the bridge without hitting netfilter

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Date:   Fri, 09 Mar 2018 10:57:24 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     dwmw2@...radead.org
Cc:     fw@...len.de, pablo@...filter.org, rga@...zon.de,
        bridge@...ts.linux-foundation.org, stephen@...workplumber.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        aliguori@...zon.com, nbd@...nwrt.org
Subject: Re: [RFC PATCH v2] bridge: make it possible for packets to
 traverse the bridge without hitting netfilter

From: David Woodhouse <dwmw2@...radead.org>
Date: Fri, 09 Mar 2018 15:31:15 +0000

> Eschewing a 15% speedup on the basis that "well, even though we've had
> three of these already for a decade, we're worried that adding a fourth
> might open the floodgates to further patches" does seem a little odd to
> me, FWIW.

The cost we are dealing with is a fundamental one which is a result of
the hook design.

Indirect calls are killer.

Indirect calls are even more killer now in the age of Spectre and
retpolines.

I definitely would rather see the fundamental issue addressed rather
than poking at it randomly with knobs for this case and that.

Thank you.