[CRIU] [PATCH] criu: add make lazy support to crit

[Adrian Reber]

On Wed, May 04, 2016 at 07:49:14PM +0300, Pavel Emelyanov wrote:
> On 04/29/2016 11:39 AM, Adrian Reber wrote:
> > From: Adrian Reber <areber at redhat.com>
> > 
> > This enables crit to remove all memory pages from a checkpoint
> > directory which can be lazily restored using userfaultfd. This
> > changes the pagemap.img and pages.img to no longer contain pages
> > which can be handled by userfaultfd (MAP_PRIVATE && MAP_ANON).
> > 
> > Usage:
> > 
> >  $ crit/crit make-lazy /tmp/4/ /tmp/5
> >  $ du -hs /tmp/4 /tmp/5
> >  201M	/tmp/4
> >  116K	/tmp/5
> > 
> > The checkpoint in /tmp/5 can be used by the actual restore process
> > and the checkpoint in /tmp/4 (with all memory pages) can be used
> > by the uffd daemon which then transfers the pages into the restored
> > on demand.
> 
> OK, but what's the use case you see for this?

To be able to remove the lazy pages from a checkpoint after the dump to
be able to restore it lazily. Also for testing, as a conformation, that
the restore actually works with all lazy pages removed.

		Adrian

> > Signed-off-by: Adrian Reber <areber at redhat.com>
> > ---
> >  crit/crit | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 78 insertions(+)
> > 
> > diff --git a/crit/crit b/crit/crit
> > index 93cbc98..0e97fe5 100755
> > --- a/crit/crit
> > +++ b/crit/crit
> > @@ -217,6 +217,75 @@ explorers = { 'ps': explore_ps, 'fds': explore_fds, 'mems': explore_mems }
> >  def explore(opts):
> >  	explorers[opts['what']](opts)
> >  
> > +def make_lazy(opts):
> > +	""" This function takes the pages from the input directory
> > +	and removes all pages which can be restored lazily.
> > +	MAP_PRIVATE && MAP_ANON and not VDSO and not VSYSCALL. """
> > +	# page size is hardcoded to 0x1000; probably a bad idea
> > +	ps = 0x1000
> > +	ps_img = pycriu.images.load(dinf(opts, 'pstree.img'))
> > +	vids = vma_id()
> > +	lazy_pages = []
> > +	for p in ps_img['entries']:
> > +		pid = p['pid']
> > +		mmi = pycriu.images.load(dinf(opts, 'mm-%d.img' % pid))['entries'][0]
> > +
> > +		print "%d" % pid
> > +
> > +		for vma in mmi['vmas']:
> > +			st = vma['status']
> > +			# 'MAP_PRIVATE', 0x2
> > +			# 'MAP_ANON',    0x20
> > +			if (vma['flags'] & 0x2) and (vma['flags'] & 0x20):
> > +				# (1 << 2) vsyscall
> > +				# (1 << 3) vdso
> > +				if not (st & (1 << 2)) and not (st & (1 << 3)):
> > +					vaddr = vma['start']
> > +					while vaddr < vma['end']:
> > +						lazy_pages.append(vaddr)
> > +						vaddr += ps
> > +
> > +		pms = pycriu.images.load(dinf(opts, 'pagemap-%d.img' % pid))
> > +		new = []
> > +
> > +		# find first pages_id
> > +		pages_id = -1
> > +		for pm in pms['entries']:
> > +			if pm.has_key('pages_id'):
> > +				pages_id = pm['pages_id']
> > +
> > +		if pages_id == -1:
> > +			# something went wrong
> > +			raise Exception('No pages_id found in pagemap!')
> > +
> > +		# open the original pages.img to remove the lazy pages
> > +		pages_in = os.path.join(opts['dir'], 'pages-%d.img' % pages_id)
> > +		pages_in = open(pages_in, 'rb')
> > +
> > +		pages_out = os.path.join(opts['outdir'], 'pages-%d.img' % pages_id)
> > +
> > +		pages_out = open(pages_out, 'wb')
> > +
> > +		for pm in pms['entries']:
> > +			if pm.has_key('pages_id'):
> > +				new.append(pm)
> > +				continue
> > +			vaddr = pm['vaddr']
> > +			i = 0
> > +			start = 0
> > +			while vaddr < pm['vaddr'] + (pm['nr_pages'] * 0x1000):
> > +				page_buffer = pages_in.read(ps)
> > +				if vaddr not in lazy_pages:
> > +					if start == 0:
> > +						start = vaddr
> > +					i +=1
> > +					pages_out.write(page_buffer)
> > +				vaddr += ps
> > +			if i != 0:
> > +				new.append({'nr_pages': i, 'vaddr': start})
> > +		pms['entries'] = new
> > +		pycriu.images.dump(pms, open(os.path.join(opts['outdir'], 'pagemap-%d.img' % pid), 'w+'))
> > +
> >  def main():
> >  	desc = 'CRiu Image Tool'
> >  	parser = argparse.ArgumentParser(description=desc,
> > @@ -267,6 +336,15 @@ def main():
> >  	show_parser.add_argument("in")
> >  	show_parser.set_defaults(func=decode, pretty=True, out=None)
> >  
> > +	# Make Lazy
> > +	lazy_parser = subparsers.add_parser('make-lazy',
> > +			help = "remove memory pages from image which can be restored lazily")
> > +	lazy_parser.add_argument('dir',
> > +			help = "criu checkpoint directory used as input")
> > +	lazy_parser.add_argument('outdir',
> > +			help = "output directory for new pages.img and pagemap.img")
> > +	lazy_parser.set_defaults(func=make_lazy)
> > +
> >  	opts = vars(parser.parse_args())
> >  
> >  	opts["func"](opts)
> >