Thanks for the quick turnaround. Good to know about the how the 2M code path differs, I have been trying to trace through some of this and it's easy to get lost between which applies to which size. Thanks! On Thu, Jun 28, 2018 at 12:03 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > On Wed 27-06-18 14:44:47, Cannon Matthews wrote: > > When booting with very large numbers of gigantic (i.e. 1G) pages, the > > operations in the loop of gather_bootmem_prealloc, and specifically > > prep_compound_gigantic_page, takes a very long time, and can cause a > > softlockup if enough pages are requested at boot. > > > > For example booting with 3844 1G pages requires prepping > > (set_compound_head, init the count) over 1 billion 4K tail pages, which > > takes considerable time. This should also apply to reserving the same > > amount of memory as 2M pages, as the same number of struct pages > > are affected in either case. > > > > Add a cond_resched() to the outer loop in gather_bootmem_prealloc() to > > prevent this lockup. > > > > Tested: Booted with softlockup_panic=1 hugepagesz=1G hugepages=3844 and > > no softlockup is reported, and the hugepages are reported as > > successfully setup. > > > > Signed-off-by: Cannon Matthews <cannonmatthews@xxxxxxxxxx> > > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > > Thanks! > > > --- > > mm/hugetlb.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index a963f2034dfc..d38273c32d3b 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -2169,6 +2169,7 @@ static void __init gather_bootmem_prealloc(void) > > */ > > if (hstate_is_gigantic(h)) > > adjust_managed_page_count(page, 1 << h->order); > > + cond_resched(); > > } > > } > > > > -- > > 2.18.0.rc2.346.g013aa6912e-goog > > -- > Michal Hocko > SUSE Labs
