linux-kernel - Re: [1/8,v3] NUMA Hotplug Emulator: add function to hide memory region via e820 table.

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Message-ID: <alpine.DEB.2.00.1011211331220.26304@chino.kir.corp.google.com>
Date:	Sun, 21 Nov 2010 13:33:40 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
cc:	Shaohui Zheng <shaohui.zheng@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, haicheng.li@...ux.intel.com,
	lethal@...ux-sh.org, Andi Kleen <ak@...ux.intel.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Haicheng Li <haicheng.li@...el.com>
Subject: Re: [1/8,v3] NUMA Hotplug Emulator: add function to hide memory
 region via e820 table.

On Sun, 21 Nov 2010, Américo Wang wrote:

> >> > > > > Index: linux-hpe4/arch/x86/kernel/e820.c
> >> > > > > ===================================================================
> >> > > > > --- linux-hpe4.orig/arch/x86/kernel/e820.c	2010-11-15 17:13:02.483461667 +0800
> >> > > > > +++ linux-hpe4/arch/x86/kernel/e820.c	2010-11-15 17:13:07.083461581 +0800
> >> > > > > @@ -971,6 +971,7 @@
> >> > > > >  }
> >> > > > >  
> >> > > > >  static int userdef __initdata;
> >> > > > > +static u64 max_mem_size __initdata = ULLONG_MAX;
> >> > > > >  
> >> > > > >  /* "mem=nopentium" disables the 4MB page tables. */
> >> > > > >  static int __init parse_memopt(char *p)
> >> > > > > @@ -989,12 +990,28 @@
> >> > > > >  
> >> > > > >  	userdef = 1;
> >> > > > >  	mem_size = memparse(p, &p);
> >> > > > > -	e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
> >> > > > > +	e820_remove_range(mem_size, max_mem_size - mem_size, E820_RAM, 1);
> >> > > > > +	max_mem_size = mem_size;
> >> > > > >  
> >> > > > >  	return 0;
> >> > > > >  }
> >> > > > 
> >> > > > This needs memmap= support as well, right?
> >> > > we did not do the testing after combine both memmap and numa=hide paramter, 
> >> > > I think that the result should similar with mem=XX, they both remove a memory
> >> > > region from the e820 table.
> >> > > 
> >> > 
> >> > You've modified the parser for mem= but not memmap= so the change needs 
> >> > additional support for the latter.
> >> > 
> >> 
> >> the parser for mem= is not modified, the changed parser is numa=, I add a addtional
> >> option numa=hide=.
> >> 
> >
> >The above hunk is modifying the x86 parser for the mem= parameter.
> >
> 
> That is fine as long as "mem=" is parsed before "numa=".
> 

If you'll read the discussion, I had no problem with modifying the mem 
parser.  I merely suggested that Shaohui modify the memmap parser in the 
same way to save max_mem_size so users can use it as well for the hidden 
nodes, that are now obsolete.  Apparently that was misunderstood by both 
of you although it looks pretty clear above, I dunno.