5 ms·

To some degree you could use a GC only language to create a large pool (eg a numpy array) and "allocate" items in there with indices as pointers. Would cover so

by janto 5y ago

To some degree you could use a GC only language to create a large pool (eg a numpy array) and "allocate" items in there with indices as pointers. Would cover some of the use cases for manual memory management. edit: scooped by a sibling comment! :) ah well, here's what you could use to structure objects in a numpy array https://numpy.org/doc/stable/user/basics.rec.html?highlight=structured%20arrays https://numpy.org/doc/stable/user/basics.rec.html?highlight=...

secondaryacct 5y ago
That s what we do in low latency java in big banks, 3 GC per day, between 5 and 6 am, anything more and 10 people are profiling.
- kaba0 5y ago
  Is that truly a good idea in case of the JVM? Of course there will be problems where this is the correct approach, but in certain cases simply letting the very advanced GC do its job is actually faster.
  - bobbylarrybobby 5y ago
    It’s not about speed (throughout) but about latency. If the GC takes (say) several minutes during a period of downtime so that it doesn’t have to run at all during uptime, then it’s worth it.
    - kaba0 5y ago
      What about ZGC then? If throughput is not the metric to optimize for, ZGC promises less than 1 ms pauses for up to TBs of heap size.
      - pjmlp 5y ago
        Java suffers from Python 2 like syndrome with Java 8. Those shops aren't going to use ZGC. Nor they will profit from the several performance improvements, including the free JIT cache across runs with PGO data on Hotspot and J9, that used to be a commercial feature on third party JDKs.
    - nextaccountic 5y ago
      What about a concurrent and parallel GC that doesn't stop the world?
cratermoon 5y ago
The author of the article mentions that trick and links to https://blog.twitch.tv/en/2019/04/10/go-memory-ballast-how-i-learnt-to-stop-worrying-and-love-the-heap-26c2462549a2/ https://blog.twitch.tv/en/2019/04/10/go-memory-ballast-how-i...
- janto 5y ago
  The link appears to be about tricking the GC into not triggering, by exploiting its threshold strategy.

by janto 5y ago

secondaryacct 5y ago

That s what we do in low latency java in big banks, 3 GC per day, between 5 and 6 am, anything more and 10 people are profiling.

kaba0 5y ago
Is that truly a good idea in case of the JVM? Of course there will be problems where this is the correct approach, but in certain cases simply letting the very advanced GC do its job is actually faster.
- bobbylarrybobby 5y ago
  It’s not about speed (throughout) but about latency. If the GC takes (say) several minutes during a period of downtime so that it doesn’t have to run at all during uptime, then it’s worth it.
  - kaba0 5y ago
    What about ZGC then? If throughput is not the metric to optimize for, ZGC promises less than 1 ms pauses for up to TBs of heap size.
    - pjmlp 5y ago
      Java suffers from Python 2 like syndrome with Java 8. Those shops aren't going to use ZGC. Nor they will profit from the several performance improvements, including the free JIT cache across runs with PGO data on Hotspot and J9, that used to be a commercial feature on third party JDKs.
  - nextaccountic 5y ago
    What about a concurrent and parallel GC that doesn't stop the world?

cratermoon 5y ago

The author of the article mentions that trick and links to https://blog.twitch.tv/en/2019/04/10/go-memory-ballast-how-i-learnt-to-stop-worrying-and-love-the-heap-26c2462549a2/ https://blog.twitch.tv/en/2019/04/10/go-memory-ballast-how-i...

janto 5y ago
The link appears to be about tricking the GC into not triggering, by exploiting its threshold strategy.