linux-kernel - Re: [tip:x86/asm] x86: Pack function addresses tightly as well

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Message-ID: <20150517073008.GA6571@gmail.com>
Date:	Sun, 17 May 2015 09:30:08 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Davidlohr Bueso <dave@...olabs.net>,
	Peter Anvin <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Brian Gerst <brgerst@...il.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Low <jason.low2@...com>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/asm] x86: Pack function addresses tightly as well


* Ingo Molnar <mingo@...nel.org> wrote:

> The median function size is around 1 cacheline (64-byte one), ~80% 
> fitting into two cachelines, with a big peak for very small 
> functions that make up something like 20% of all functions [...]

Correction:

   32% of kernel functions fit into a single cacheline,
   55% fit into two cachelines,
   70% into three cachelines,
   76% into four cachelines

so the tail is longer than my quick read of the graph suggested.

OTOH, probability of use is biased towards smaller functions: we tend 
to use smaller, facility functions more frequently.

Thanks,

	Ingo
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