linux-kernel - Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags

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Message-Id: <1241032436.938.1519.camel@calx>
Date:	Wed, 29 Apr 2009 14:13:56 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 5/5] proc: export more page flags in /proc/kpageflags

On Wed, 2009-04-29 at 16:05 +0800, Wu Fengguang wrote:
> On Wed, Apr 29, 2009 at 01:49:21AM +0800, Matt Mackall wrote:
> > On Tue, 2009-04-28 at 09:09 +0800, Wu Fengguang wrote:
> > > plain text document attachment (kpageflags-extending.patch)
> > > Export 9 page flags in /proc/kpageflags, and 8 more for kernel developers.
> > 
> > My only concern with this patch is it knows a bit too much about SLUB
> > internals (and perhaps not enough about SLOB, which also overloads
> > flags). 
> 
> Yup. PG_private=PG_slob_free is not masked because SLOB actually does
> not set PG_slab at all. I wonder if it's safe to do this change:
> 
>         /* SLOB */
> -       PG_slob_page = PG_active,
> +       PG_slob_page = PG_slab,
>         PG_slob_free = PG_private,

Yep.

> In the page-types output:
> 
>          flags  page-count       MB  symbolic-flags                     long-symbolic-flags
> 0x000800000040        7113       27  ______A_________________P____      active,private
> 0x000000000040          66        0  ______A______________________      active
> 
> The above two lines are obviously for SLOB pages.  It indicates lots of
> free SLOB pages. So my question is:

Free here just means partially allocated.

> - Do you have other means to get the nr_free_slobs info? (I found none in the code)
> or
> - Will exporting the SL*B overloaded flags going to help?

Yes, it's useful.

-- 
http://selenic.com : development and support for Mercurial and Linux


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