Re: [PATCH] mm: make free_bootmem to loop bdata_list

From: KAMEZAWA Hiroyuki
Date: Thu Mar 13 2008 - 22:01:20 EST


On Thu, 13 Mar 2008 18:39:34 -0700
"Yinghai Lu" <yhlu.kernel@xxxxxxxxx> wrote:

> On Thu, Mar 13, 2008 at 6:39 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> > On Thu, 13 Mar 2008 11:53:31 -0700
> > "Yinghai Lu" <yhlu.kernel@xxxxxxxxx> wrote:
> > > ===================================================================
> > > --- linux-2.6.orig/mm/bootmem.c
> > > +++ linux-2.6/mm/bootmem.c
> > > @@ -427,7 +438,9 @@ int __init reserve_bootmem(unsigned long
> > >
> > > void __init free_bootmem(unsigned long addr, unsigned long size)
> > > {
> > > - free_bootmem_core(NODE_DATA(0)->bdata, addr, size);
> > > + bootmem_data_t *bdata;
> > > + list_for_each_entry(bdata, &bdata_list, list)
> > > + free_bootmem_core(bdata, addr, size);
> > > }
> >
> >
> > Just a confirmation.
> > In above loop, boundary check in free_bootmem_core() hits two or more times ?
> > If yes, it's ok.
> > If no, please exit loop at hit.
>
> yes. need that handle range cross node (RAMDISK case that is end
> beyond end_of_ram).
>
Then, <addr, size> can spread across nodes.

IMHO, there are *big* memory hole between nodes in some systems.
This kind of interface, which allows alloc/free bootmem accross nodes,
will see terrible trouble when a programmer assumes "alloc/free bootmem
always return contiguous size of memory" (This is guaranteed now,)

Does the new allocator (you changed ?) guarantee that returned <address, size>
is fully contiguous even if it spreads accross nodes ?

If no, NACK for this version.

Thanks,
-Kame


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