Integrated: 8344414: ZGC: Another division by zero in rule_major_allocation_rate

Tue Dec 3 10:45:46 UTC 2024

On Tue, 19 Nov 2024 07:18:20 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> This specific issue was known since #20888.  As well as a more serious issue in `calculate_extra_young_gc_time` which may introduce a `NaN`. This specific issue is sane as long as we have IEEE 754 sans the C++ standard making division by zero UB.
> 
> As discussed in #21304 it is probably better to try and tackle the division by zero issue by making sure the input is never zero. This patch introduces a small offset to the average which will effectively leave the value unchanged unless it is zero, and behave as almost zero in calculations without causing actual division by zero.
> 
> There is still the issue with `NaN`, this patch adds a short circuit when this can occur and returns the analytical result of the calculation.

This pull request has now been integrated.

Changeset: 63af2f42
Author:    Axel Boldt-Christmas <aboldtch at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/63af2f42b7abe9504897d7c3f3b4cc0b57123694
Stats:     28 lines in 3 files changed: 11 ins; 1 del; 16 mod

8344414: ZGC: Another division by zero in rule_major_allocation_rate

Reviewed-by: eosterlund, stefank

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PR: https://git.openjdk.org/jdk/pull/22228