Re: [PATCH] mm: skip if required_kernelcore is larger than totalpages

[Tang Chen]

Hi, Qiu

The patch seems OK to me. Only one little concern below.

On 10/12/2015 09:37 AM, Xishi Qiu wrote:
> On 2015/10/9 23:41, Yasuaki Ishimatsu wrote:
>
> > On Thu, 8 Oct 2015 10:21:05 +0800
> > Xishi Qiu <qiuxishi@xxxxxxxxxx> wrote:
> >
> > > If kernelcore was not specified, or the kernelcore size is zero
> > > (required_movablecore >= totalpages), or the kernelcore size is larger
> > Why does required_movablecore become larger than totalpages, when the
> > kernelcore size is zero? I read the code but I could not find that you
> > mention.
> If user only set boot option movablecore, and the value is larger than
> totalpages, the calculation of kernelcore is zero, but we can't fill
> the zone only with kernelcore, so skip it.
>
> I have send a patch before this patch.
> "fix overflow in find_zone_movable_pfns_for_nodes()"
> 		...
>   		required_movablecore =
>   			roundup(required_movablecore, MAX_ORDER_NR_PAGES);
> +		required_movablecore = min(totalpages, required_movablecore);
>   		corepages = totalpages - required_movablecore;
> 		...


So if required_movablecore >= totalpages, there won't be any ZONE_MOVABLE.
How about add a warning or debug info to tell the user he has specified a
too large movablecore, and it is ignored ?

Thanks.


> Thanks,
> Xishi Qiu
>
> > Thanks,
> > Yasuaki Ishimatsu
> >
> > > than totalpages, there is no ZONE_MOVABLE. We should fill the zone
> > > with both kernel memory and movable memory.
> > >
> > > Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
> > > ---
> > >   mm/page_alloc.c | 7 +++++--
> > >   1 file changed, 5 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > index af3c9bd..6a6da0d 100644
> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -5674,8 +5674,11 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> > >   		required_kernelcore = max(required_kernelcore, corepages);
> > >   	}
> > >   
> > > -	/* If kernelcore was not specified, there is no ZONE_MOVABLE */
> > > -	if (!required_kernelcore)
> > > +	/*
> > > +	 * If kernelcore was not specified or kernelcore size is larger
> > > +	 * than totalpages, there is no ZONE_MOVABLE.
> > > +	 */
> > > +	if (!required_kernelcore || required_kernelcore >= totalpages)
> > >   		goto out;
> > >   
> > >   	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
> > > --
> > > 2.0.0
> > >
> > >
> > > --
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> > .
>
>
> .

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