RFR(S): 8007036: G1: Too many old regions added to last mixed GC
bengt.rutisson at oracle.com
Mon Mar 4 03:59:17 PST 2013
(Happened to send an empty mail just before. Here's what I wanted to write.)
Sorry for not reviewing this earlier!
Changes look good, ship it!
One question. You added a note to the _length field in CollectionSetChooser:
// The number of candidate old regions added to the CSet chooser.
// Note: this is not updated when removing a region using
// remove_and_move_to_next() below.
As far as I can tell we should really decrement the _length field in
remove_and_move_to_next(). Would it maybe be better to fix this (as a
separate change of course) than to add the note? I guess the code works
since we don't use the length information after finlalize_cset() but it
feels a bit fragile.
On 2/26/13 7:28 PM, John Cuthbertson wrote:
> Hi Everyone,
> I've only received (and incorporated) comments from Vitaly Davidovich
> so I'm pinging the list again. Any takers? It's quite small - the main
> part of the fix is in G1CollectorPolicy::finalize_cset().
> On 1/29/2013 1:35 PM, John Cuthbertson wrote:
>> Hi Everyone,
>> Here's a new webrev based upon feedback from Vitaly:
>> On 1/28/2013 1:59 PM, John Cuthbertson wrote:
>>> Hi Everyone,
>>> Can I have a couple of volunteers look over the changes for this CR?
>>> The webrev is at: http://cr.openjdk.java.net/~johnc/8007036/webrev.0/
>>> When adding old regions to the collection set we don't take into
>>> account whether the old regions added so far take us below the
>>> G1HeapWastePercent. As a result we could end up adding (and
>>> collecting) many more regions than we needed to. The actual number
>>> added was the minimum between the number of candidate regions /
>>> G1MixedGCCountTarget and 10% of the heap.
>>> Currently the calculation of the reclaimable bytes as a percentage
>>> of the uses exact arithmetic. It might make sense, at some point in
>>> the future, to use inexact arithmetic (rounding) in the decision on
>>> whether to continue mixed GCs and use exact arithmetic when adding
>>> As part of this change I've also moved a couple routines from
>>> CollectionSetChooser to G1CollectorPolicy. I think they "fit" better
>>> in G1CollectorPolicy.
>>> GCOld with tenuring threshold = 1 and a marking threshold = 10.
>>> Many thanks to Monica for identifying the issue.
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