RFR (S): 8195115: G1 Old Gen MemoryPool CollectionUsage.used values don't reflect mixed GC results
mandy.chung at oracle.com
Mon Jan 29 18:35:20 UTC 2018
Thanks for the reply Paul. Try to understand a little more on the
specific from gc-specific memory pool you depend on.
On 1/29/18 8:27 AM, Hohensee, Paul wrote:
> A name change would affect Amazon’s heap monitoring, and thus I expect
> it would affect other users as well.
> As long as there are gc-specific memory pools, we’re going to need to
> be able to identify them, and right now that’s done via name.
MemoryPoolMXBean::getType returns "heap" memory type for GC-specific
memory pools. Are you using this method? Do you use the name to build
in specific characteristic of a memory pool (e.g. eden vs old gen)?
> All the mxbeans are identified by name, so that’s a general design
> principle. The only way I can think of to get rid of name dependency
> would be to figure out what abstract metrics users want to monitor and
> implement them for all collectors. HeapUsage (instantaneous occupancy)
> is one, CollectionUsage (long-lived occupancy) is another, both of
> these for the entire heap, not just particular memory pools.
The sum of HeapUsage and CollectionUsage of all heap memory pools was
expected to give an incorrect approximation for the entire heap usage.
Are you seeing issue/bug with the sum result?
> That said, imo there will always be a demand for the ability to get
> collector and memory pool specific details, so I don’t see a way to
> get around providing named entities.
> *From: *mandy chung <mandy.chung at oracle.com>
> *Organization: *Oracle Corporation
> *Date: *Friday, January 26, 2018 at 2:38 PM
> *To: *"Hohensee, Paul" <hohensee at amazon.com>, Erik Helin
> <erik.helin at oracle.com>, David Holmes <david.holmes at oracle.com>
> *Cc: *"serviceability-dev at openjdk.java.net"
> <serviceability-dev at openjdk.java.net>,
> "hotspot-gc-dev at openjdk.java.net" <hotspot-gc-dev at openjdk.java.net>
> *Subject: *Re: RFR (S): 8195115: G1 Old Gen MemoryPool
> CollectionUsage.used values don't reflect mixed GC results
> On 1/25/18 1:04 PM, Hohensee, Paul wrote:
> > The JMX API spec doesn’t specify what the memory pool or garbage >
> collector names are, but the current names are de-facto part of the >
> API, so if we change the existing ones, imo a CSR should be filed.
> The names are implementation details but I can see how an application
> might be impacted if they depend on it. CSR approval is not strictly
> necessary while I think filing one to document the change would be
> Does the name change impact any application you know of? I'm trying to
> understand if any improvement to API is needed so that applications
> don't need to depend on the names.
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