linux-kernel - Re: [PATCH v2] consolidate WARN

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Message-Id: <4F4C93520200007800075197@nat28.tlf.novell.com>
Date:	Tue, 28 Feb 2012 07:41:54 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] consolidate WARN_...ONCE() static variables

>>> On 28.02.12 at 01:03, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Mon, 27 Feb 2012 15:10:34 +0000
> "Jan Beulich" <JBeulich@...e.com> wrote:
> 
>> Due to the alignment of following variables, these typically consume
>> more than just the single byte that 'bool' requires, and as there are
>> a few hundred instances, the cache pollution (not so much the waste of
>> memory) sums up. Put these variables into their own section, outside
>> of any half way frequently used memory range.
>> 
>> v2: Do the same also to the __warned variable of rcu_lockdep_assert().
>> (Don't, however, include the ones used by printk_once() and alike, as
>> they can potentially be hot.)
> 
> I have a bad feeling that I still don't understand this patch.  Ho hum.
> 
> What are the rules for the new .data.unlikely section?  When should
> people put variables into this section?  Perhaps we can document this
> somewhere?

If I knew the "where" part of this, I could put together a few sentences.
I just grep-ed through Documentation/, without finding e.g. any rules
or guidelines for using {,un}likely()...

Jan

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