Hi, I did an experiment described above. I created a patch with pre-touch [1] and started a JVM with an option -XX:+AlwaysPreTouch and configured Ignite with equal values for initial and max sizes for each data region. I did several runs. I observed JVM crash dumps [2], [3]. Also it is easy to observe JVM OOM-killed.
[1] https://github.com/apache/ignite/pull/5220 [2] https://gist.github.com/pavlukhin/e5e6605e9b43666266667ba8d1aab42f#file-hs_err_pid5763-log [3] https://gist.github.com/pavlukhin/e5e6605e9b43666266667ba8d1aab42f#file-hs_err_pid6411-log вт, 30 окт. 2018 г. в 9:19, Павлухин Иван <vololo...@gmail.com>: > Hi guys, > > I am not aware that it is possible to run JVM in "allocation-free" fashion. > If you know that it is possible please share it. As I know JVM allocates > memory out of garbage collectable area for internal purposes like JIT, > GC itself. Also native built-it code can request memory allocation from OS, > e.g. zip facilities. If we imagine that system is running under memory > allocation > which is close to a limit then even small allocation request can fail and > lead > to OOM killing. > > But I think that a simple and useful thing that could be done first is > making > an experiment. As Andrey mentioned > > AFAIK, Ignite always pre-touch first region. So, you can try to set > region > > MAX size equal to MIN and get region allocated on node start. > If it is so then it should not be hard to launch Ignite and observe it > running > very close to OS memory limit with Java heap and Ignite off-heap > pre-touched. > After that one could check whether it is possible to observe Ignite OOM > killed. > Let's say my bet is that it is relatively easy to catch OOM here. > > What do you think? > > пт, 26 окт. 2018 г. в 18:18, Yakov Zhdanov <yzhda...@apache.org>: > >> Andrey, >> >> Probability of a OOM kill will be much lower if offheap is pretouched. >> What >> do you mean by JVM internal needs? In my understanding if user enables >> option to pretouch heap and fixes the heap to prevent jvm releasing memory >> back to OS, then OOM killing is very unlikely. >> >> I would agree that pretouch for offheap may be helpful in many cases. >> >> --Yakov >> > > > -- > Best regards, > Ivan Pavlukhin > -- Best regards, Ivan Pavlukhin
