CRIU

So, several features that use memory changes tracking are finally working in CRIU tool! Sad news is that the respective kernel changes are still in -mm tree, so our kernel with applied patches should be used instead.That said, meet the incremental ... [More] dumps (http://criu.org/Incremental_dumps)and iterative migration (http://criu.org/Iterative_migration)! [Less]

The 0.5 is out!No new cool features, that work on Linux-3.9, since we mostly focused on bug fixing (thanks to all who played with the tool and reported those to us), but with the custom kernel (patches are expected to get merged into Linux-3.10) we ... [More] can do various new things, like incremental snapshots, C/R netlink sockets and a little bit more :)Have fun! And sorry in advance if we are not very responsive in the nearest days -- there are long holidays in Russia in the beginning of May. [Less]

So, Andrew Morton has merged into his tree kernel patches, that help us to monitor how tasks change their memory! What it gives to +CRIU ? Quite a lot.For example right now we have a --snapshot option for crtools, that allows us to take incremental ... [More] dump from a process tree, that was dumped previously. For example, for a VNC server with mplayer playing a movie, the size of first dump is 39M, while the second   (incremental) dump taken in 30 seconds after it weights "only" 8.2M.Another reason why we wanted this is so called "iterative migration" -- in this type of live migration we first copy all tasks' memory on the destination node, then freeze the processes and copy only what has changed. With this the freeze time for e.g. the vnc+mplayer on 100Mb network would decrease from 4 seconds to less than one (and even less, if we do more than one "iteration").The feature is very new and not yet finished (and not yet documented :)), but what we already have is great. If the kernel patches will happen to be in v3.10 that would be awesome! [Less]

Some numbers concerning optimized freeze time with the help memory tracking. We have a test in zdtm test suite, which creates a big mapping (512 Mb) and populates it with pages. This test is used to demonstrate how memory tracking can speed dumping ... [More] huge apps.First, we start this test and just dump it. The freeze time is 7.7 seconds, 7.6 of which criu writes pages into image file.The 2nd experiment is two step -- first we use criu pre-dump action, that grabs memory from task, turns memory changes tracking, unfreezes task and only after this starts writing its memory into image file. After this we perform regular dump, asking criu not to dump pages, that hasn't changed since previous dump (well, pre-dump). In this scenario the timings are much more application-friendly :) The total freeze time is 0.1 second (0.05 for pre-dump and 0.05 for dump steps) since the big time (~7 sec) spent for wiring pages into images it done while application is running.If we look at the image file, that describes memory pages layout (pagemap.img) we'd see, that after pre-dump we have 8 regions 16384 pages each (512 Mb), while the update on this image, created on dump stage would show, that we have all those pages present in "parent" image set, just as expected :)This test is in criu source tree -- the test/mem-snap/run-predump-2.sh script is quite small and does all the above steps. [Less]

Some small improvement for the "exec" command. Now it also supports syscalls' argument, in which kernel puts some data back, e.g. the 2nd argument to the read() system call. To do this provide the "@" arg in the command line in the respective place.See http://criu.org/Remote_syscall_execution for details.

Great news!There's a new vzctl in +OpenVZ that is now integrated with the CRIU tool. So from now on, you can easily live-migrate containers on vanilla kernel v3.9 and above :)Have fun!

After +Andrey Wagin +LVEE visit and +CRIU talk I continued my experiments with criu. Frankly speaking it happens only from time to time, last time was on LinuxCon Europe 2012 in Barcelona, after meeting with +Kirill Kolyshkin  and +Pavel ... [More] Emelyanov.So:+.Gentoo already have criu package, just a bit outdated, I opened ticket and propose ebuild for new version.+ Basically it works for me, and I found one useful idea for day-to-day desktop usage. Now if I forget to run some long task in screen, criu helps me to "move" process inside screen - emerge for example.- Strange errors like: (00.003742) Error (sk-unix.c:313): Can't stat socket 11846(./tmp/ksocket-max_posedon/krunnerwX2343.slave-socket): No such file or directorySo, visiting conferences is a excellent type for spending time, and I'm inviting everybody to next LVEE.  [Less]

My proposal to talk about +CRIU on LinuxCon North America has been accepted!  :)This time I plan not just talk about what we would the project to do, but about what it actually does and how these features are used in real life.

Great news! The memory changes tracking patches are merged within the 3.11 merge window!Looking forward to fool-blooded incremental snaphots and iterative live migration in criu-0.7 + linux-3.11 pair.

We've recently received a lot of feedback from people who (try to) use CRIU. This feedback was summarized and added on the "usage scenarios" page on our wiki. Interestingly, that quite a lot of them are about applications debugging and analysis.Thank's everyone who helps us move the project further!