RFE: Add compressed oops to VM info string
david.holmes at oracle.com
Mon Nov 14 17:10:25 PST 2011
On 14/11/2011 9:22 PM, Krystal Mok wrote:
> Printing flags isn't good enough in some scenarios.
> Take jmap -heap for example. HeapSummary prints out a few flags of
> interest, but it can be misleading for people who don't know that not
> all flags are in effect all the time.
> In , MaxNewSize shows "17592186044415 MB", and OldSize shows "5439488
> (5.1875MB)". Neither of these values correspond to the actual heap
> stats; they just act as a hint to let ergonomics make the decision.
> PrintFlagsFinal won't do any good in this kind of scenario (and
> PrintCommandLineFlags won't show anything).
As I said if the print-flags option isn't showing the compressed-oops
flag settings then that should be fixed.
Sorry I don't understand the connection to your jmap -heap example.
> Kris Mok
> : https://gist.github.com/1363195
> On Sat, Nov 12, 2011 at 7:53 AM, Srinivas Ramakrishna <ysr1729 at gmail.com
> <mailto:ysr1729 at gmail.com>> wrote:
> +1 to David's (and others') suggestion:-
> I agree that +PrintFlagsFinal makes this less subjective and more
> -- ramki
> On Thu, Nov 10, 2011 at 1:31 PM, David Holmes
> <david.holmes at oracle.com <mailto:david.holmes at oracle.com>> wrote:
> In case I didn't mention it earlier there is also
> -Xinternalversion which might be extended this way.
> But personally I think printing the flags is the way to go, and
> if the desired flags are not printed then that is a RFE for the
> print-flags options.
> On 11/11/2011 4:02 AM, Mandy Chung wrote:
> FWIW. Kumar added an internal option -XshowSettings to the
> launcher in
> JDK 7 to print various VM and java settings. This could be a
> place to include "compressed oops" and other VM ergonomic
> setting in. It
> takes an optional suboption "all, vm, properties, locale".
> $ java -XshowSettings:vm
> VM settings:
> Stack Size: 320.00K
> Max. Heap Size (Estimated): 910.00M
> Ergonomics Machine Class: server
> Using VM: Java HotSpot(TM) Server VM
> java -XshowSettings -version doesn't print the additional
> information. I
> haven't spent time looking into the reason why.
> On 11/10/11 08:01, Paul Hohensee wrote:
> I don't think the version string is the place for
> dumping ergo
> decision results,
> rather I agree with David Holmes and Joe that
> or some other switch should be used. We shouldn't have
> "mixed mode",
> etc. in the
> string either, but given that they're there we're kinda
> stuck with them.
> The reason we have "Server" and "Client" (and "Embedded,
> btw) is to
> builds that are statically different. Tiered got folded
> into Server
> awhile ago, which
> is why it's no longer mentioned in the version string.
> Changing the version string is a non-trivial thing to
> do: it has to go
> an approval process because it's a supported public
> interface. There
> are, e.g.,
> quite a few version string parsers out there that
> wouldn't take kindly
> to change.
> On 11/10/11 8:18 AM, Volker Simonis wrote:
> +1 from me
> On Thu, Nov 10, 2011 at 12:44 PM, Christian Thalinger
> <christian.thalinger at oracle.__com
> <mailto:christian.thalinger at oracle.com>> wrote:
> On Nov 10, 2011, at 12:16 PM, Volker Simonis wrote:
> Hi Kris,
> first I want to say that I like and support
> your enhancement request.
> However once we do this, if would suggest
> printing other
> information as well.
> Particularly the fact if we're using tiered
> compilation comes to my
> mind here.
> I would therefore suggest to use a less
> verbose "compressed oops"
> string and also
> print the concrete compressed oops mode
> that's actually used
> (unscaled, zerobased, heapbased).
> This information may be particularly usefull
> because it may change
> depending on the users heap setting
> and the current system memory situation.
> So finally, we could use something like:
> OpenJDK 64-Bit Server VM (build
> 20.0-b11-internal, mixed mode, tiered,
> Honestly I don't know what it takes to change
> that string since it's
> a public known option. But my personal opinion
> is: print the most
> important runtime settings like JIT mode, GC
> used, compressed oops
> mode. Something along these lines:
> Java HotSpot(TM) Server VM (build 23.0-b03,
> mixed mode, tiered,
> serial gc, zerobased coops)
> Just my two cents...
> -- Chris
> For such a version string, it would be
> probably better to construct
> the string on the fly, otherwise
> the 'info_strs' struct you are currently
> using may become too big.
> What are your opinions?
> On Thu, Nov 10, 2011 at 8:54 AM, Krystal
> Mok<rednaxelafx at gmail.com
> <mailto:rednaxelafx at gmail.com>>
> Hi all,
> I'd like to propose to add "compressed
> oops" to the VM info
> string, so that
> people using "java -version" can get a
> better understanding of the
> ergonomics of the VM.
> I've posted a patch , against hsx20's
> master. The files
> modified are
> still pretty much the same on
> hotspot-main's master.
> With the patch applied, "java -version"
> may show:
> OpenJDK 64-Bit Server VM (build
> 20.0-b11-internal, mixed mode,
> and what used to work still works:
> OpenJDK Client VM (build
> 20.0-b11-internal, mixed mode, sharing)
> P.S. Alibaba (Taobao)'s OCA is submitted
> already, still waiting
> for approval
> from Oracle.
> Kris Mok
> Software Engineer, Taobao
> : https://gist.github.com/__1354299
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