Re: Can't boot guest with more than 3585MB when using large pages

Marcelo Tosatti
2009-03-25T16:11:05Z

On Tue, Mar 24, 2009 at 04:57:46PM -0500, Ryan Harper wrote:
> * Alex Williamson <alex.williamson@hp.com> [2009-03-24 16:07]:
> >
> > On a 2.6.29, x86_64 host/guest, what's special about specifying a guest
> > size of -m 3586 when using -mem-path backed by hugetlbfs? 3585 works,
> > 3586 hangs here:
> >
> > ...
> > PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
> > Placing 64MB software IO TLB between ffff880020000000 - ffff880024000000
> > software IO TLB at phys 0x20000000 - 0x24000000
> > Memory: 3504832k/4196352k available (2926k kernel code, 524740k absent, 166780k reserved, 1260k data, 496k init)
> >
> > I can back -mem-path by tmpfs or disk and it works fine. Also works
> > with no -mem-path, but it would obviously be nice to benefit from large
> > pages on big guests. The system has plenty of huge pages to back the
> > request, and booting with -mem-prealloc makes no difference. Tested on
> > latest git as of today. Thanks,
>
> I've seen this as well, haven't had a chance to dig into the issue yet
> either. Certainly can test patches if anyone has an idea of what's
> wrong here.

Can you strace and see if the mmap on hugetlbfs is correctly sized?