Re: post-copy is broken?

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Li, Liang Z (liang.z.li@intel.com) wrote:
> > > > > I've run it directly, setting relevant QTEST_QEMU_BINARY.
> > > >
> > > > Interesting; it's failing reliably for me - but only with a
> > > > reasonably freshly booted machine (so that the pages get THPd).
> > >
> > > The same here. Freshly booted machine with 64GiB ram. I've checked
> > > /proc/vmstat: huge pages were allocated
> > 
> > Thanks for testing.
> > 
> > Damn; this is confusing now.  I've got a RHEL7 box with 4.6.0-rc3 on where it
> > works, and a fedora24 VM where it fails (the f24 VM is where I did the bisect
> > so it works fine with the older kernel on the f24 userspace in that VM).
> > 
> > So lets see:
> >    works: Kirill's (64GB machine)
> >           Dave's RHEL7 host (24GB RAM, dual xeon, RHEL7 userspace and kernel
> > config)
> >    fails: Dave's f24 VM (4GB RAM, 4 vcpus VM on my laptop24 userspace and
> > kernel config)
> > 
> > So it's any of userspace, kernel config, machine hardware or hmm.
> > 
> > My f24 box has transparent_hugepage_madvise, where my rhel7 has
> > transparent_hugepage_always (but still works if I flip it to madvise at run
> > time).  I'll try and get the configs closer together.
> > 
> > Liang Li: Can you run my test on your setup which fails the migrate and tell
> > me what your userspace is?
> > 
> > (If you've not built my test yet, you might find you need to add a :
> >    tests/postcopy-test$(EXESUF): tests/postcopy-test.o
> > 
> >   to the tests/Makefile)
> > 
> 
> Hi Dave,
> 
>   How to build and run you test? I didn't do that before.

Apply the code in:
http://lists.gnu.org/archive/html/qemu-devel/2016-04/msg02138.html

fix the:
+            if ( ((b + 1) % 255) == last_byte && !hit_edge) {
to:
+            if ( ((b + 1) % 256) == last_byte && !hit_edge) {

to tests/Makefile
   tests/postcopy-test$(EXESUF): tests/postcopy-test.o

and do a:
    make check

in qemu.
Then you can rerun the test with:
    QTEST_QEMU_BINARY=path/to/qemu-system-x86_64 ./tests/postcopy-test

if it works, reboot and check it still works from a fresh boot.

Can you describe the system which your full test failed on? What distro on
the host? What type of host was it tested on?

Dave

> 
> Thanks!
> Liang
> 
> > 
> > Dave
> > >
> > > --
> > >  Kirill A. Shutemov
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

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