On Wed, 13 May 2015 01:44:22 +0000 Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> wrote:
> > > order = huge_page_order(h);
> > > VM_BUG_ON(!IS_ALIGNED(start_pfn, 1 << order));
> > > + VM_BUG_ON(order == UINT_MAX);
> > > for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << order)
> > > dissolve_free_huge_page(pfn_to_page(pfn));
> >
> > Do we need to calculate this each time? Can it be done in
> > hugetlb_init_hstates(), save the result in a global?
>
> Yes, it should work. How about the following?
> This adds 4bytes to .data due to a new global variable, but reduces 47 bytes
> .text size of code reduces, so it's a win in total.
>
> text data bss dec hex filename
> 28313 469 84236 113018 1b97a mm/hugetlb.o (above patch)
> 28266 473 84236 112975 1b94f mm/hugetlb.o (below patch)
Looks good. Please turn it into a real patch and send it over when
convenient?
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -40,6 +40,7 @@ int hugepages_treat_as_movable;
> int hugetlb_max_hstate __read_mostly;
> unsigned int default_hstate_idx;
> struct hstate hstates[HUGE_MAX_HSTATE];
> +unsigned int minimum_order __read_mostly;
static.
And a comment would be nice ;)
>
> ...
>
> @@ -1626,11 +1621,16 @@ static void __init hugetlb_init_hstates(void)
> {
> struct hstate *h;
>
> + minimum_order = UINT_MAX;
Do this at compile time.
> for_each_hstate(h) {
> + if (minimum_order > huge_page_order(h))
> + minimum_order = huge_page_order(h);
> +
> /* oversize hugepages were init'ed in early boot */
> if (!hstate_is_gigantic(h))
> hugetlb_hstate_alloc_pages(h);
> }
> + VM_BUG_ON(minimum_order == UINT_MAX);
Is the system hopelessly screwed up when this happens, or will it still
be able to boot up and do useful things?
If the system is hopelessly broken then BUG_ON or, better, panic should
be used here. But if there's still potential to do useful things then
I guess VM_BUG_ON is appropriate.
> }
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