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From Andrey Mashenkov <andrey.mashen...@gmail.com>
Subject Re: Pre-touch for Ignite off-heap memory
Date Wed, 24 Oct 2018 08:25:42 GMT
Docs [1] says, that OOM can also be thrown when native library can't
allocate memory chunk if physical memory (ram + swap).

>> Shouldn't OOM happen if you're trying to allocate beyond the virtual
memory capacity (beyond X GB)?
With 64-bit addressing you have some exabytes of virtual memory, is it
possible to have such amount of physical memory?

I'd think JVM process should be killed by OS much earlier due to memory
overcommit. See [2].

[1]
https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/memleaks002.html
[2]
http://engineering.pivotal.io/post/virtual_memory_settings_in_linux_-_the_problem_with_overcommit/

On Wed, Oct 24, 2018 at 7:12 AM Denis Magda <dmagda@apache.org> wrote:

> Alex,
>
> Correct me if I'm wrong, but even if an OS runs out of physical memory (X
> GB in total) an Ignite node process still can request the X GB from virtual
> memory. Yes, virtual memory can involve swapping and disk to satisfy your
> request but this shouldn't be a reason of the OOM. Shouldn't OOM happen if
> you're trying to allocate beyond the virtual memory capacity (beyond X GB)?
>
> Denis
>
> On Tue, Oct 23, 2018 at 12:08 PM Gerus <agerus@gridgain.com> wrote:
>
> > Hi *Igniters*,
> > Some time ago I've raised a suggestion for product improvement
> > https://issues.apache.org/jira/browse/IGNITE-9112
> > <https://issues.apache.org/jira/browse/IGNITE-9112>  .  It's all about
> > off-heap memory allocation. Current implementation can have some
> > improvements for failure critical systems. Ignite can have OOM in
> runtime,
> > because RAM can be used by OS, if it will not be pre-booked by operation
> > system and this proposal is to address that. Common case is offheap and
> > thats why memory segment cannot be managed by JVM that has
> +AlwaysPreTouch
> > option
> > Obviously this implementation will make startup longer and thats why it
> is
> > proposed to use configuration flag to manage this feature
> > I think, it will be useful to have this option. Are you supporting this?
> >
> >
> >
> > --
> > Sent from: http://apache-ignite-developers.2346864.n4.nabble.com/
> >
>


-- 
Best regards,
Andrey V. Mashenkov

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