linux-kernel - Re: [PATCH] x86: introduce bootmem

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Date:	Fri, 6 Mar 2009 20:36:11 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	yinghai@...nel.org, tglx@...utronix.de, hpa@...or.com,
	penberg@...helsinki.fi, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: introduce bootmem_state -v2


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Fri, 6 Mar 2009 20:12:49 +0100
> Ingo Molnar <mingo@...e.hu> wrote:
> 
> > 
> > * Yinghai Lu <yinghai@...nel.org> wrote:
> > 
> > > 
> > > Impact: cleanup
> > > 
> > > extend after_bootmem and after_init_bootmem to bootmem_state
> > > and will have BEFORE_BOOTMEM, DURING_BOOTMEM, AFTER_BOOTMEM
> > > 
> > > v2: style changes according to ingo
> > > 
> > > Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> > > 
> > > ---
> > >  arch/x86/kernel/setup.c |    1 +
> > >  arch/x86/mm/init.c      |   13 +++++++------
> > >  arch/x86/mm/init_32.c   |   28 ++++++++++++++++++++--------
> > >  arch/x86/mm/init_64.c   |   33 +++++++++++++++++++--------------
> > >  include/linux/mm.h      |    9 +++++++++
> > >  5 files changed, 56 insertions(+), 28 deletions(-)
> > 
> > > Index: linux-2.6/include/linux/mm.h
> > > ===================================================================
> > > --- linux-2.6.orig/include/linux/mm.h
> > > +++ linux-2.6/include/linux/mm.h
> > > @@ -1067,6 +1067,15 @@ extern void __init mmap_init(void);
> > >  extern void show_mem(void);
> > >  extern void si_meminfo(struct sysinfo * val);
> > >  extern void si_meminfo_node(struct sysinfo *val, int nid);
> > > +
> > > +enum bootmem_state {
> > > +	BEFORE_BOOTMEM,
> > > +	DURING_BOOTMEM,
> > > +	AFTER_BOOTMEM
> > > +};
> > > +
> > > +extern enum bootmem_state bootmem_state;
> > > +
> > >  extern int after_bootmem;
> > 
> > Btw., the after_bootmem variable itself should either move to 
> > x86 (and arch/sh), or should be defined in mm/bootmem.c.
> > 
> > Right now we have this weird mm.h construct that is not actually 
> > useful to generic code.
> > 
> > Andrew, what would be your preference?
> > 
> 
> If two architectures are using it then it should be provided 
> by core kernel?
> 
> This is obvious if the state transitions are occurring in 
> core-kernel code, but if the transitions are happening in arch 
> code then making it a core concept assumes consistency between 
> different architectures which might not exist.
> 
> IOW: dunno.

Core kernel could provide a wrapper allocator which calls the 
right method depending on which state we are in. It will call 
bootmem_alloc() if called early, and kmalloc() if called later. 
Or something like that. Would there be any utility in that?

	Ingo
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