linux-kernel - Re: [PATCH v8 4/4] printk: allow increasing the ring buffer depending on the number of CPUs

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Message-Id: <20140626162014.156f6741c7d9d3234879054f@linux-foundation.org>
Date:	Thu, 26 Jun 2014 16:20:14 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	gregkh@...uxfoundation.org, hpa@...ux.intel.com,
	linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
	Stephen Warren <swarren@...dotorg.org>,
	Michal Hocko <mhocko@...e.cz>, Petr Mladek <pmladek@...e.cz>,
	Joe Perches <joe@...ches.com>,
	Arun KS <arunks.linux@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Davidlohr Bueso <davidlohr@...com>,
	Chris Metcalf <cmetcalf@...era.com>
Subject: Re: [PATCH v8 4/4] printk: allow increasing the ring buffer
 depending on the number of CPUs

On Fri, 27 Jun 2014 01:16:30 +0200 "Luis R. Rodriguez" <mcgrof@...e.com> wrote:

> > > Another note --  since this option depends on SMP and !BASE_SMALL technically 
> > > num_possible_cpus() won't ever return something smaller than or equal to 1
> > > but because of the default values chosen the -1 on the compuation does affect
> > > whether or not this will trigger on > 64 CPUs or >= 64 CPUs, keeping the
> > > -1 means we require > 64 CPUs.
> > 
> > hm, that sounds like more complexity.
> > 
> > > This all can be changed however we like but the language and explained logic
> > > would just need to be changed.
> > 
> > Let's start out simple.  What's wrong with doing
> > 
> > 	log buf len = max(__LOG_BUF_LEN, nr_possible_cpus * per-cpu log buf len)
> 
> Sure, you already took in the patch series though so how would you like to
> handle a respin, you just drop the last patch and we respin it?

A fresh patch would suit.  That's if you think it is a reasonable 
approach - you've thought about this stuff more than I have!
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