[talk] Python

[Edward Capriolo]

The java class file format is well documented. Basically one pointer to the
runtime class of the object followed by the object.

If a given language is reference counted each object has one extra atomic
field to count references.

If a given language does not have objects but instead uses maps (that
repeat the fields evey instance) that is going to be a more large object in
memory.

While i am not a large expert in this i believe javas approach is like a c
struct with the exception the first word size bytes are a pointer to the
type of class so that instances can be runtime inspected.

Java also has a very clever system for compressing 64 bit pointers.. see
compressedOOPs option. I have not heard much of this optimization anywhere
else.

On Thursday, April 28, 2016, Sujit K M <kmsujit at gmail.com> wrote:

> > Anecdotal. Keep in mind I have tested this and you can create 'a lot more
> > objects' given the same RAM than many other popular non java languages.
> :)
>
> Could you please clarify further? I mean does it involve a object size
> on the JVM.
> How to measure the size occupied by the Object? How much extra space the
> JVM
> needs? What is JDK Feature that Let's you claim this?
>
> I have serious questions regarding this claim. As Interpreted or JIT
> compiled languages
> should in reality occupy more space.
>
> >
> > On Wed, Apr 27, 2016 at 4:13 PM, Pete Wright <pete at nomadlogic.org
> <javascript:;>> wrote:
> >>
> >>
> >>
> >> On 04/26/2016 03:56 AM, Brian Coca wrote:
> >>>
> >>> As many a Java dev has told me: "the only problem is that you did not
> >>> install enough RAM, just add it, it's cheap!"
> >>>
> >>>
> >>
> >> and therein is the issue - in practice i've found that by adding more
> >> memory to a JVM heap will tend to worsen GC pauses, especially for
> latency
> >> sensitive operations.  then you get to do all sorts of fun stuff like
> >> storing cached objects outside of the JVM or lord knows what.
> >>
> >> i spent about 3 months trying to help a team tune their java app when
> they
> >> noticed it would periodically show latencies of several seconds. they
> kept
> >> adding more memory to the heap, which made things worse.  once we
> turned on
> >> debugging metrics for GC it became painfully apparent that due to the
> huge
> >> heap that they had allocated GC was taking ages to complete and
> stopping to
> >> world in the process.  good times :)
> >>
> >> -pete
> >>
> >> --
> >> Pete Wright
> >> pete at nomadlogic.org <javascript:;>
> >>
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> >
> >
> >
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