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

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Date:	Wed, 15 Apr 2009 15:57:49 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC][PATCH] proc: export more page flags in /proc/kpageflags

> That's pretty good separations. I guess it would be convenient to make the
> extra kernel flags available under CONFIG_DEBUG_KERNEL?

Yes.

BTW an alternative would be just someone implementing a suitable
command/macro in crash(1) and tell the kernel hackers to run that on
/proc/kcore. That would have the advantage to not require code.

> > > > > > - PG_compound
> > 
> > I would combine these three into a pseudo "large page" flag.
> 
> Very neat idea! Patch updated accordingly.
>  
> However - one pity I observed:
> 
> # ./page-areas 0x008000
>     offset      len         KB
>       3088        4       16KB
> 
> We can no longer tell if the above line means one 4-page hugepage, or two
> 2-page hugepages... Adding PG_COMPOUND_TAIL into the CONFIG_DEBUG_KERNEL block

There's only a single size (2 or 4MB), at worst two.

> > 
> > PG_poison is also useful to export. But since it depends on my
> > patchkit I will pull a patch for that into the HWPOISON series.
> 
> That's not a problem - since the PG_poison line is be protected by
> #ifdef CONFIG_MEMORY_FAILURE :-) 

Good point. I added a patch to only add it to my pile,
but I can drop that again.

-Andi
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