gortiz commented on PR #16912:
URL: https://github.com/apache/pinot/pull/16912#issuecomment-3617398358
> Trying to understand the change. When -XX:-G1UseAdaptiveIHOP is not set,
does it prevent per-thread memory/CPU utilization from being reported? Per the
argument name, seems they are unrelated
@Jackie-Jiang I think the PR description is wrong. `-G1UseAdaptiveIHOP`
doesn't affect whether we can estimate the amount of allocated memory. The
reason we need it is that if the % of used memory is below IHOP, the JVM won't
collect old generation. The OOM protection algorithm assumes the % of used
memory is mostly alive memory, but as long as the % of memory is below IHOP,
the used memory may be mostly garbage. As a result, if our thresholds are
smaller than IHOP, we may be throttling or killing queries while the % of alive
memory is actually very low. With adaptive IHOP, the actual % of memory that
fires old GCs is undefined.
I think what we should do here is to verify that the IHOP is lower than our
thresholds. This means:
- If the JVM uses adaptive IHOP, the check should fail
- If the JVM doesn't use IHOP:
- If IHOP is higher than our thresholds, the check should fail
- In other case, the check should succeed.
If the check fails, we should log an error message and continue working as
before (ie if the check was executed during startup, run without OOM
protection, if the check failed when a config was changed, log an error and
continue using the old config)
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