netdev - RE: [PATCH net] x86: bpf_jit: fix compilation of large bpf programs

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Date:	Tue, 26 May 2015 15:47:19 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Eric Dumazet' <eric.dumazet@...il.com>
CC:	'Alexei Starovoitov' <ast@...mgrid.com>,
	"David S. Miller" <davem@...emloft.net>,
	Daniel Borkmann <daniel@...earbox.net>,
	Eric Dumazet <edumazet@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net] x86: bpf_jit: fix compilation of large bpf programs

From: Eric Dumazet 
> Sent: 26 May 2015 16:30
> 
> > Yes, interesting, a benchmark that manages to run a lot of code 'cold cache'.
> 
> We have binaries here at Google with 400 or 500 MBytes of text.
> 
> Not benchmark, super real workloads you know.

Indeed, and a lot of the code is likely to be running 'cold cache'.

I was alluding to the problem where people will benchmark a small function
by running in 1000s of times in a tight loop with exactly the same data.
Not only is it 'hot cache' but any dynamic branch prediction is 'trained'
to the specific data.

	David