linux-kernel - Re: [PATCH 5/5] lockdep: pack subclass/trylock/read/check into a single argument

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Message-ID: <20140121172737.GA24896@redhat.com>
Date:	Tue, 21 Jan 2014 18:27:37 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Dave Jones <davej@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] lockdep: pack subclass/trylock/read/check into a
	single argument

On 01/21, Peter Zijlstra wrote:
>
> I tried the below but filed to see my vmlinux shrink, maybe I'm just not
> building the right kernel, or otherwise GCC is stupid.

...

> +struct lockdep_acquire_flags {
> +	unsigned long subclass : 3;
> +	unsigned long trylock  : 1;
> +	unsigned long read     : 2;
> +	unsigned long check    : 1;
> +};

Yes, I tried this too. I do see the difference, but the result is worse:

	- 5262832
	+ 5256987

looks like, gcc is not smart enough...

Oleg.

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