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

Américo Wang
2010-11-21T13:57:50Z

On Sat, Nov 20, 2010 at 04:45:06PM -0800, David Rientjes wrote:
>On Fri, 19 Nov 2010, Shaohui Zheng 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=".

I think "mem=" should always be parsed before "numa=" no matter what
order they are specified in cmdline, since we need know how much total
memory we have at first.

Thanks.