Leo Li wrote:
Hi,Egor:
On 14 Sep 2006 12:30:49 +0700, Egor Pasko <[EMAIL PROTECTED]> wrote:
On the 0x1E4 day of Apache Harmony Leo Li wrote:
> Hi,all:
> As we all know, java objects are allocated on heap instead of
stack,
> thus there is a problem about how to garbage collect short-lived
objects
> quickly.
> In a recent real project I involved, a server built on java
tries to
> send thousands of messages to client per second. A lot of short-lived
> messages is created as objects and discarded. (Although I can recycle
these
> memory, there is still a byte array created during per call of nio
read
and
> write.) Since current GC strategy adopted by current RI starts to work
only
> when the memory allocated approaching the limit of java heap, the work
of GC
> is huge and will raise a wave on the server performance. Furthermore,
after
> a long run, although I know GC will merge memory, the operating system
> reports there is memory fragment and in the worst case the OS will
even
> report real memory is exhausted.
> Of course it is possible to limit the java heap so as to force gc
> frequently as a workround, is it preferrable to collect short-lived
objects
> quickly such as adopt aged-related object queues as one of the gc
strategy?
what about forcing gc by hand? does it help?
Forcing gc by hand does work, but it is difficult for code to know
when to
call gc.So I think it is better if VM can give some support since it
knows
the global situation.:)
..and of course a manual gc() call does not necessarily result in a gc -
there's
no guarantee - so even if it was the right time, you might not get it.
Regards,
Oliver
What about the VMs here, drlvm or J9?
In a DRLVM JIT (Jitrino.OPT) there is an escape analysis prototype. It
detects objects that can be allocated on stack (and, hence, on
registers). Currently, it is switched off by default, and, when
enabled, it just marks the objects that are not escaped. This info is
never used in Jitrino.OPT yet. Sometimes, escape analyzers help, but
not very much :)
It will be great if JIT can help to allocation objects on stack.
DRLVM GC gurus will say more ;)
--
Egor Pasko, Intel Managed Runtime Division
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--
Oliver Deakin
IBM United Kingdom Limited
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