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High G1 Old GC frequency

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Chinese perch posted this in #questions
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Chinese perchOP
hi, my g1 old gc seems to be called a lot more frequent than usual with noticeable pauses > 1.5 seconds. i think the issue is just running out of memory but wanted to get second thoughts in case its something else.

https://spark.lucko.me/RwrntKSRHY
Philippine Crocodile
well, I have a pretty good idea why
image.png
it's likely constantly working with swap memory (which is slow af)
reduce your xmx to like 8gb
it's not likely you will need more, and what you need is more free memory
@Philippine Crocodile it's not likely you will need more, and what you need is more free memory
Chinese perchOP
i don't think the swap was affecting the heap but idk could be wrong. theres still 1gb~ free for the OS so oom killer shouldn't come in even if we disable swap.
it ended up being not enough heap memory after all
went up to 11-13gb heap allocated after i gave it 16gb
Chinese perchOP
okay nvm, adding more ram to relieve memory pressure didn't help rip. its not a ram issue. idk why g1 old gc is being called so frequently. https://spark.lucko.me/XFPra6O78I might try swapping to zgc
Tamz
how come no jvm flags?
image.png
Chinese perchOP
aikar wasn't doing much to relieve it
Tamz
Tried zgc generational?
Chinese perchOP
yeah thats my next step with zgc
i just dont know why g1 old is being called so frequently
Tamz
well you have a XMS of 128
try to match with XMX and see what happens
but lower your max ram by 1.5g first and restart
@Tamz try to match with XMX and see what happens
Chinese perchOP
it still had high g1 old freq when it was set the same with the older flags here

https://spark.lucko.me/RwrntKSRHY
Tamz
:hmm: interesting
unfortunately, im not a flags guy
Chinese perchOP
yeah no worries, im confused too lol
might just have to do zgc
ty
Philippine Crocodile
do a spark report with --alloc
might want to do it with --thread *
and for the love of everything, reduce the xmx so you're sure swap is not being used for the server
@Philippine Crocodile and for the love of everything, reduce the xmx so you're sure swap is not being used for the server
Chinese perchOP
its not the xmx, this is an entirely different machine lol
but i'll try with alloc and thread ty
Darthmineboy
Well the answer may surprise you. It looks like a plugin is calling GC manually every 3 minutes. Try adding -XX:+DisableExplicitGC to the flags to prevent this
stupid lag fixers making lag worse 😉
@Darthmineboy Well the answer may surprise you. It looks like a plugin is calling GC manually every 3 minutes. Try adding -XX:+DisableExplicitGC to the flags to prevent this
Chinese perchOP
wait really? that could actually explain it. how were you able to tell through spark?
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