Deallocating memory pages

Jon Masamitsu jon.masamitsu at oracle.com
Mon Jan 28 17:01:50 UTC 2013



On 01/25/13 15:12, Hiroshi Yamauchi wrote:

...
> In server applications, this sort of workload variations can happen 
> for reasons such as capacity redundancy and 
> time-of-day variations, etc. On desktops, one might keep open all 
> sorts of applications at the same time such as web browsers, developer 
> tools, graphics tools, etc. but might put significant workload (or a 
> temporary memory usage increase) on only one application at a time. In 
> such an environment, if an application that was running with high 
> workload in the past can release some RAM, it'd be much nicer for 
> other applications.
>
>
>     2) applications with many objects larger than a page so that freeing
>     those objects could free memory.
>
>
> Yes, but objects don't necessarily have to be larger than a page as 
> long as free chunks that are left after they are freed get coalesced 
> together into a free chunk that's larger than a page.

So when a coalesced page gets added back to the free lists it can deallocate
memory even if the neither of the objects coalesced was greater than a
page in size.  Cool.

Do you see any increase in the sweeping times?  Or the young gen
collection times?

You mention that you don't deallocate the headers of objects on the free 
list.
Was that because you tried deallocation that included the headers and that
was worse?

I'll get feedback from the other GC guys and let you know what we
want to do.

Jon
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/attachments/20130128/19401c95/attachment.htm>


More information about the hotspot-gc-dev mailing list