netdev - Re: [PATCH] net: filter: Convert the BPF VM to threaded code

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Message-ID: <20110730095520.GA12248@electric-eye.fr.zoreil.com>
Date:	Sat, 30 Jul 2011 11:55:20 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Rui Ueyama <rui314@...il.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: filter: Convert the BPF VM to threaded code

Rui Ueyama <rui314@...il.com> :
> The result of benchmark looks good.

So far the overall improvement is below 2% (upper bound, without calculator).

And the result of benchmark without tcpdump looks strange.

> A simple benchmark that sends 10M UDP
> packets to lo took 76.24 seconds on average on Core 2 Duo L7500@...GHz.when
> tcpdump is running. With this patch it took 75.41 seconds, which means we save
> 80ns for each packet on that processor.

You forgot to analyze the figures without tcpdump.

> I think converting the VM to threaded code is low hanging fruit, even
> if we'd have JIT compilers for popular architectures. Most of the lines
> in my patch are indentation change, so the actual change is not big.

Without further data nor plan for future / possible improvements, it
could be said a gratuitous rewrite too.

-- 
Ueimor
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