linux-kernel - Re: [PATCH 1/5] rcusync: introduce struct rcu_sync

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Message-ID: <20131004153012.19245adb@gandalf.local.home>
Date:	Fri, 4 Oct 2013 15:30:12 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] rcusync: introduce struct rcu_sync_ops

On Fri, 4 Oct 2013 12:12:25 -0700
Linus Torvalds <torvalds@...ux-foundation.org> wrote:


>  - together with using a few inline functions, suddenly the "indirect"
> jumps through this type descriptor end up actually being nice direct
> compile-time constants: iow, they get turned into direct jumps.

As all the rcu_synchronization() methods (on non UP) are quite
expensive, I doubt that this optimization is worth anything.

> 
> Tadaa. You actually get good code generation, and you use *less*
> dynamic memory since you don't have to have this pointer to the
> descriptor.

Getting rid of the extra dynamic memory and the pointer business, on the
other hand, does make your suggestion worth doing.

-- Steve

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