linux-kernel - Re: [PATCH 1/4] rcu: Speed up calling of RCU tasks callbacks

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Message-ID: <20180523213553.7a0ffd6d@gandalf.local.home>
Date:   Wed, 23 May 2018 21:35:53 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Joel Fernandes <joelaf@...gle.com>,
        linux-kernel@...r.kernel.org, Peter Zilstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>, byungchul.park@....com,
        kernel-team@...roid.com, Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 1/4] rcu: Speed up calling of RCU tasks callbacks

On Wed, 23 May 2018 17:51:19 -0700
Joel Fernandes <joel@...lfernandes.org> wrote:

> Shouldn't this assignment be done outside the loop? I believe the variable
> will be initialized on each iteration.
> 
> A program like this doesn't terminate:
> 
> #include<stdio.h>
> 
> int main() {
> 	for (;;) {
> 		int i = 10;
> 		if (!(i--))
> 			break;
> 	}
> 
> 	return 0;
> }

Hey, it compiled, booted and tested. SHIP IT! ;-)

But yeah, a little egg on my face for that one. I blame it for the
first code I wrote right off of coming back from vacation.

> 
> Otherwise looks good to me, I would initialize fract to 10 so its consistent
> with "HZ/10" in other parts of the code but I'm ok with either number.

I was thinking about that, but for some reason I thought 15. Not sure
why. I'm fine with dropping it down to 10. I'll send out a more proper
patch tomorrow.

Thanks!

-- Steve