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

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Message-Id: <20120228001210.26b59479.akpm@linux-foundation.org>
Date:	Tue, 28 Feb 2012 00:12:10 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Jan Beulich" <JBeulich@...e.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] consolidate WARN_...ONCE() static variables

On Tue, 28 Feb 2012 08:02:40 +0000 "Jan Beulich" <JBeulich@...e.com> wrote:

> >>> On 28.02.12 at 08:44, Andrew Morton <akpm@...ux-foundation.org> wrote:
> > On Tue, 28 Feb 2012 07:41:54 +0000 "Jan Beulich" <JBeulich@...e.com> wrote:
> > 
> >> >>> 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()...
> >>
> > 
> > At the definition site in vmlinux.lds?
> 
> Sorry, Andrew, but this makes no sense to me.

I really don't care - anywhere you like.  Just the darn changelog, if
nowhere else.

I still don't have an answer to my question :( Some statement
describing what the new section is *for*.  Seems a pretty important
thing?


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