Re: [PATCH] alpha: switch to NO_BOOTMEM

From: Michal Hocko
Date: Fri Jun 29 2018 - 05:44:07 EST


On Fri 29-06-18 12:24:00, Mike Rapoport wrote:
> On Thu, Jun 28, 2018 at 05:38:29AM +0800, kbuild test robot wrote:
> > Hi Mike,
> >
> > I love your patch! Yet something to improve:
> >
> > [auto build test ERROR on linus/master]
> > [also build test ERROR on v4.18-rc2 next-20180627]
> > [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> >
> > url: https://github.com/0day-ci/linux/commits/Mike-Rapoport/alpha-switch-to-NO_BOOTMEM/20180627-194800
> > config: alpha-allyesconfig (attached as .config)
> > compiler: alpha-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
> > reproduce:
> > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > chmod +x ~/bin/make.cross
> > # save the attached .config to linux build tree
> > GCC_VERSION=7.2.0 make.cross ARCH=alpha
> >
> > All error/warnings (new ones prefixed by >>):
> >
> > mm/page_alloc.c: In function 'update_defer_init':
> > >> mm/page_alloc.c:321:14: error: 'PAGES_PER_SECTION' undeclared (first use in this function); did you mean 'USEC_PER_SEC'?
> > (pfn & (PAGES_PER_SECTION - 1)) == 0) {
> > ^~~~~~~~~~~~~~~~~
> > USEC_PER_SEC
>
> The PAGES_PER_SECTION is defined only for SPARSEMEM with the exception of
> x86-32 defining it for DISCONTIGMEM as well. That said, any architecture
> that can have DISCTONTIGMEM=y && NO_BOOTMEM=y will fail the build with
> DEFERRED_STRUCT_PAGE_INIT enabled.
>
> The simplest solution seems to make DEFERRED_STRUCT_PAGE_INIT explicitly
> dependent on SPARSEMEM rather than !FLATMEM. The downside is that deferred
> struct page initialization won't be available for x86-32 NUMA setups.

I am really dubious that 32b systems really need DEFERRED_STRUCT_PAGE_INIT.
Regardless of the memory mode. Those systems simply do not have enough
memory to bother. Deferred initialization is targeting much larger
beasts.
--
Michal Hocko
SUSE Labs
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