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Groups > comp.lang.java.programmer > #5734
| From | Michal Kleczek <kleku75@gmail.com> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Why "lock" functionality is introduced for all the objects? |
| Date | 2011-06-28 18:41 +0200 |
| Organization | http://onet.pl |
| Message-ID | <iud083$2jr$1@news.onet.pl> (permalink) |
| References | <d0bb9e06-16f0-4282-a37e-47e9ca9630ec@r2g2000vbj.googlegroups.com> <iuce66$2nh$1@news.albasani.net> |
Lew wrote:
> Alex J wrote:
>> I'm curious why Java designers once decided to allow every object to
>> be lockable (i.e. [sic] allow using lock on those).
>
> Because that makes it possible to do concurrent programming intrinsically.
>
Could you elaborate more on that?
Do you mean there is no other way to do it?
I find this question quite intriguing as well since it looks quite useless
for example to be able to lock on java.lang.Integer instance (and it is
strange for me that java.lang.Integer instance occupies much more memory as
int). Surely a compromise must have been done taking into account various
language features ("synchronized" keyword, lack of multiple inheritance,
lack of closures) - but I am not that knowlegeable enough to explain this
compromise in detail.
>> I know, that out of such a design decision every Java object contain
>> lock index, i.e. new Object() results in allocation of at least 8
>> bytes where 4 bytes is object index and 4 bytes is lock index on 32-
>> bit JVM.
>> I think that it just inefficient waste of space, because not all the
>> objects requires to be lockable/waitable.
>
> Well, that's your opinion.
>
It is not only his opinion - the size of object header is important
especially on memory constrained devices. But not only - there is a reason
why UseCompressedOops flag was introduced in 64 bit HotSpot JVM.
>> The better decision, IMHO, would be to introduce lock/wait mechanics
>> for only, say, the Lockable descendants.
>
> Oh, yeah, your opinion is humble.
>
>> The current approach seems to be very simple, but is the performance
>> penalty so small for not be taken into an account?
>
> Yes. Nonexistent, really.
>
I wouldn't say so - see:
http://wikis.sun.com/display/HotSpotInternals/CompressedOops
Especially the sentence:
"Memory is pretty cheap, but these days bandwidth and cache is in short
supply"
--
Michal
Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar
Why "lock" functionality is introduced for all the objects? Alex J <vstrength@gmail.com> - 2011-06-28 02:29 -0700
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 07:33 -0400
OT "sic" (was Re: Why "lock" functionality is introduced for all the objects? blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-28 15:56 +0000
Re: OT "sic" (was Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 12:19 -0400
Re: Why "lock" functionality is introduced for all the objects? Michal Kleczek <kleku75@gmail.com> - 2011-06-28 18:41 +0200
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 13:10 -0400
Re: Why "lock" functionality is introduced for all the objects? Michal Kleczek <kleku75@gmail.com> - 2011-06-28 19:53 +0200
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 14:13 -0400
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-28 14:23 -0400
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 14:33 -0400
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-28 14:52 -0400
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 16:20 -0400
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-29 00:53 -0400
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-29 01:04 -0400
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-29 01:43 -0400
Re: Why "lock" functionality is introduced for all the objects? Patricia Shanahan <pats@acm.org> - 2011-06-28 11:42 -0700
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-28 14:54 -0400
Re: Why "lock" functionality is introduced for all the objects? Patricia Shanahan <pats@acm.org> - 2011-06-28 12:34 -0700
Re: Why "lock" functionality is introduced for all the objects? markspace <-@.> - 2011-06-28 13:20 -0700
Re: Why "lock" functionality is introduced for all the objects? Patricia Shanahan <pats@acm.org> - 2011-06-28 13:44 -0700
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-29 01:05 -0400
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 16:21 -0400
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-29 01:06 -0400
Re: Why "lock" functionality is introduced for all the objects? BGB <cr88192@hotmail.com> - 2011-06-28 14:30 -0700
Re: Why "lock" functionality is introduced for all the objects? Robert Klemme <shortcutter@googlemail.com> - 2011-06-29 18:56 +0200
Re: Why "lock" functionality is introduced for all the objects? BGB <cr88192@hotmail.com> - 2011-06-28 13:43 -0700
Re: Why "lock" functionality is introduced for all the objects? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-28 20:43 -0400
Re: Why "lock" functionality is introduced for all the objects? BGB <cr88192@hotmail.com> - 2011-06-28 21:14 -0700
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-06-29 01:12 -0400
Re: Why "lock" functionality is introduced for all the objects? Joshua Maurice <joshuamaurice@gmail.com> - 2011-07-01 18:28 -0700
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-02 00:19 -0400
Re: Why "lock" functionality is introduced for all the objects? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-07-01 19:05 -0700
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-02 00:26 -0400
Re: Why "lock" functionality is introduced for all the objects? BGB <cr88192@hotmail.com> - 2011-07-04 09:39 -0700
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-05 02:11 -0400
Re: Why "lock" functionality is introduced for all the objects? Alex J <vstrength@gmail.com> - 2011-07-05 16:56 -0700
Re: Why "lock" functionality is introduced for all the objects? "John B. Matthews" <nospam@nospam.invalid> - 2011-07-06 00:57 -0400
Re: Why "lock" functionality is introduced for all the objects? supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 05:55 -0400
Re: Why "lock" functionality is introduced for all the objects? Lew <noone@lewscanon.com> - 2011-06-28 14:40 -0400
Re: Why "lock" functionality is introduced for all the objects? Robert Klemme <shortcutter@googlemail.com> - 2011-06-29 19:15 +0200
Re: Why "lock" functionality is introduced for all the objects? Tom Anderson <twic@urchin.earth.li> - 2011-06-30 23:04 +0100
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-06-30 18:29 -0400
Re: Why "lock" functionality is introduced for all the objects? Patricia Shanahan <pats@acm.org> - 2011-06-30 17:05 -0700
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-06-30 20:17 -0400
Re: Why "lock" functionality is introduced for all the objects? Tom Anderson <twic@urchin.earth.li> - 2011-07-01 21:22 +0100
Re: Why "lock" functionality is introduced for all the objects? Tom Anderson <twic@urchin.earth.li> - 2011-07-01 21:40 +0100
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-01 18:08 -0400
Re: Why "lock" functionality is introduced for all the objects? BGB <cr88192@hotmail.com> - 2011-07-05 12:15 -0700
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-05 15:30 -0400
Re: Why "lock" functionality is introduced for all the objects? blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-05 21:10 +0000
Re: Why "lock" functionality is introduced for all the objects? BGB <cr88192@hotmail.com> - 2011-07-05 22:08 -0700
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-06 05:57 -0400
Re: Why "lock" functionality is introduced for all the objects? blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-06 17:07 +0000
Re: Why "lock" functionality is introduced for all the objects? Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-07 04:08 +1000
Re: Why "lock" functionality is introduced for all the objects? blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-06 19:09 +0000
Re: Why "lock" functionality is introduced for all the objects? Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-07 09:26 +1000
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-06 20:25 -0400
Re: Why "lock" functionality is introduced for all the objects? blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-07 19:37 +0000
Re: Why "lock" functionality is introduced for all the objects? blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-07 19:35 +0000
Re: Why "lock" functionality is introduced for all the objects? Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-07 14:34 -0700
OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-08 17:19 +0000
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-09 05:41 +1000
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-08 19:58 +0000
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) lewbloch <lewbloch@gmail.com> - 2011-07-08 13:45 -0700
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-10 01:50 -0400
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-10 19:15 +0000
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) KitKat <kitkat_11697@gmail.example.com> - 2011-07-10 18:38 -0400
Re: OT names/nyms/etc. (was Re: Why "lock" functionality is introduced for all the objects?) KitKat <kitkat_11697@gmail.example.com> - 2011-07-09 00:29 -0400
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-09 00:26 -0400
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-06 20:05 -0400
Re: Why "lock" functionality is introduced for all the objects? Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-07 10:24 +1000
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-06 21:52 -0400
Re: Why "lock" functionality is introduced for all the objects? Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-07 12:43 +1000
Re: Why "lock" functionality is introduced for all the objects? KitKat <kitkat_11697@gmail.example.com> - 2011-07-06 23:00 -0400
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