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SubjectRe: [PATCH] mm: fix boundary checking in free_bootmem_core
On Thu, Mar 13, 2008 at 2:59 PM, Andi Kleen <ak@suse.de> wrote:
> On Thursday 13 March 2008 02:22:40 Andrew Morton wrote:
> > On Wed, 12 Mar 2008 18:11:41 -0700 "Yinghai Lu" <yhlu.kernel@gmail.com> wrote:
> >
> > > > <looks at it>
> > > >
> > > > Sorry, but I find the changelog very hard to amke sense of. I presently
> > > > have:
> > > >
> > > >
> > > > So call it when numa is enabled, we don't know which node have that
> > > > range. and make it more robust.
> > > >
> > > > Try to trim it to get valid sidx, and eidx.
> > > >
> > > > Could you please expand on this?
> > >
> > > please check following...
> > >
> >
> > Heaps better, thanks ;) Below is what I now have.
> >
> > (cc's people)
> >
> > Guys, could you please review this? Maybe test it a bit?
> >
> > Thanks.
> >
> >
> > From: "Yinghai Lu" <yhlu.kernel@gmail.com>
> >
> > With numa enabled, some callers could have a range o fmemory on one node but
> > try to free that on other node. This can cause some pages to be freed
> > wrongly.
>
> Concrete examples?
>
> If that happens it's really just a problem that the bootmem API
> is wrong. I was always annoyed by the hardcoded NODE_DATA(0)s in
> free_bootmem.
>
> I would suggest if that happens you just fix free_bootmem to search
> for the correct node instead of hardcoding 0 and then eliminate
> free_bootmem_node() everywhere and replace it with free_bootmem()
>
> >
> > For example: when we try to allocate 128g boot ram early for gart/swiotlb, and
> > free that range later so gart/swiotlb can get some range afterwards.
>
> I'm confused by the example. AFAIK there is no memory freeing in either
> gart nor swiotlb. At least there wasn't until very recently.

For big system when numa=off or disabled, vmemmap will use 3.6g ram
when you have 256g. if you don't allocate the PMD continuous.

then i tried to reserve 64M or 128M RAM before that, and free that
before gart/switotble try to allloc_bootmem under 4g.

that patch will make the system without ram on node0 not happy.
because of free_bootmem is hardcoded to use node0.

>
>
> >
> > With this patch, we don't need to care which node holds the range, just loop
> > to call free_bootmem_node for all online nodes.
> >
> > This patch make free_bootmem_core() more robust by trimming the sidx and eidx
> > according the ram range that the node has.
>
> I think you should just kill free_bootmem_node() and replace it everywhere
> with your improved free_bootmem()

using phys_to_nid()? it seems we only have that on x86_64.

also there is assumpation that reserve_bootmem_node, reserver_bootmem
can not cross the nodes.
I want to remove that constrient too.


YH


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