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microsoft / gctoolkit

Tool for parsing GC logs
https://github.com/microsoft/gctoolkit
MIT License
1.25k stars 155 forks source link

ZGC missing data #381

Open AlinaHovakimyan opened 2 months ago

AlinaHovakimyan commented 2 months ago

ZGC missing data: # Safepoints

DestroyDetachedPages, PrepareRelocationSet from concurrent times

mark summary (Mark: 1 stripe(s), 2 proactive flush(es), 1 terminate flush(es), 1 completion(s), 0 continuation(s) )

nMethods (registered/unregistered)

References

Metaspace: parsing exists but most probably has some bug, so comes as null

relocation info

dsgrieve commented 2 months ago

@AlinaHovakimyan - all of this is quite possible. We didn't exhaustively capture all data. Mostly we're looking at the data that helps tune gc behavior and some of these (like mark stripe, etc) aren't useful to for tuning in our opinion. We can be wrong about this and maybe you know what to do with this data. We welcome your input here.

AlinaHovakimyan commented 2 months ago

@dsgrieve we do agree that this infos are not that commonly used, but we often see cases in low-latency applications (such as trading) where every ms of a pause matters. It's always helpful to get as granular insights as possible into why the pause takes as much as it takes to help diagnosis of what can be improved, even e.g. in the application code.