2008-06-02 17:58:41

by Luck, Tony

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Subject: RE: [patch 01/41] cpu_alloc: Increase percpu area size to 128k

> The per cpu allocator requires more per cpu space and we are already near
> the limit on IA64. Increase the maximum size of the IA64 per cpu area from
> 64K to 128K.

> -#define PERCPU_PAGE_SHIFT 16 /* log2() of max. size of per-CPU area */
> +#define PERCPU_PAGE_SHIFT 17 /* log2() of max. size of per-CPU area */

Don't you need some more changes to the alt_dtlb_miss handler in
ivt.S for this to work? 128K is not a supported pagesize on any
processor model.

-Tony


2008-06-02 23:51:36

by Rusty Russell

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Subject: Re: [patch 01/41] cpu_alloc: Increase percpu area size to 128k

On Tuesday 03 June 2008 03:58:17 Luck, Tony wrote:
> > The per cpu allocator requires more per cpu space and we are already near
> > the limit on IA64. Increase the maximum size of the IA64 per cpu area
> > from 64K to 128K.
> >
> > -#define PERCPU_PAGE_SHIFT 16 /* log2() of max. size of per-CPU area */
> > +#define PERCPU_PAGE_SHIFT 17 /* log2() of max. size of per-CPU area */
>
> Don't you need some more changes to the alt_dtlb_miss handler in
> ivt.S for this to work? 128K is not a supported pagesize on any
> processor model.

Yes, this was one of the issues with IA64 and extending the per-cpu area.
It's probable that the IA64 TLB nailing trick might have to give way for
dynamic per-cpu...

Rusty.

2008-06-10 17:22:53

by Christoph Lameter

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Subject: RE: [patch 01/41] cpu_alloc: Increase percpu area size to 128k

On Mon, 2 Jun 2008, Luck, Tony wrote:

> > The per cpu allocator requires more per cpu space and we are already near
> > the limit on IA64. Increase the maximum size of the IA64 per cpu area from
> > 64K to 128K.
>
> > -#define PERCPU_PAGE_SHIFT 16 /* log2() of max. size of per-CPU area */
> > +#define PERCPU_PAGE_SHIFT 17 /* log2() of max. size of per-CPU area */
>
> Don't you need some more changes to the alt_dtlb_miss handler in
> ivt.S for this to work? 128K is not a supported pagesize on any
> processor model.

Ok so this needs to be 18?

2008-06-10 19:54:55

by Luck, Tony

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Subject: RE: [patch 01/41] cpu_alloc: Increase percpu area size to 128k

> > > -#define PERCPU_PAGE_SHIFT 16 /* log2() of max. size of per-CPU area */
> > > +#define PERCPU_PAGE_SHIFT 17 /* log2() of max. size of per-CPU area */
> >
> > Don't you need some more changes to the alt_dtlb_miss handler in
> > ivt.S for this to work? 128K is not a supported pagesize on any
> > processor model.
>
> Ok so this needs to be 18?

Yes. 18 will work (256K is an architected page size, guaranteed to be supported
by all processor models ... SDM 2:52 table 4-4).

-Tony