Integrated: 8257901: ZGC: Take virtual memory usage into account when sizing heap

[Per Liden]

On Tue, 8 Dec 2020 13:41:56 GMT, Per Liden <pliden at openjdk.org> wrote:

> MaxVirtMemFraction limits the amount of address space the GC should use for the heap. This is used by the heuristics in Arguments::set_heap_size() to select an appropriate default max heap size. However, that heuristic can select a max heap size that will not fit with ZGC, since ZGC uses additional address space (for multi-mapping and the virtual-to-physical ratio). As a result, if the address space is limited, and -Xmx is not specified, then ZGC might refuse to start with the error:
> 
> "Failed to reserve enough address space for Java heap"
> 
> I propose we abstract MaxVirtMemFraction to make it configurable for each GC, so that the heuristics in Arguments::set_heap_size() will pick a default max heap size that also works for ZGC.
> 
> Testing: Manual testing using different ulimit -v sizes.

This pull request has now been integrated.

Changeset: 0a0691eb
Author:    Per Liden <pliden at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/0a0691eb
Stats:     38 lines in 7 files changed: 24 ins; 0 del; 14 mod

8257901: ZGC: Take virtual memory usage into account when sizing heap

Reviewed-by: stefank, eosterlund, ayang, tschatzl

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PR: https://git.openjdk.java.net/jdk/pull/1696