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From nokia ceph <nokiacephus...@gmail.com>
Subject Too many Cassandra threads waiting!!!
Date Wed, 01 Aug 2018 07:08:12 GMT
Hi,

i'm having a 5 node cluster with cassandra 3.0.13.

i could see the cassandra process has too many threads.

*# pstree -p `pgrep java` | wc -l*
*453*

And almost all of those threads are in *sleeping* state and wait at
*# cat  /proc/166022/task/1698913/wchan*
*futex_wait_queue_me*

Some more info:
*# strace -e trace=all -p 166022*
*strace: Process 166022 attached*
*futex(0x7efc24aeb9d0, FUTEX_WAIT, 166023, NULL*

# cat /proc/166022/stack
[<ffffffff810f5126>] futex_wait_queue_me+0xc6/0x130
[<ffffffff810f5deb>] futex_wait+0x17b/0x280
[<ffffffff810f7b26>] do_futex+0x106/0x5a0
[<ffffffff810f8040>] SyS_futex+0x80/0x180
[<ffffffff816b4fc9>] system_call_fastpath+0x16/0x1b
[<ffffffffffffffff>] 0xffffffffffffffff


What is the reason cassandra is having these many threads? is it the normal
behavior of cassandra?  Is there a way to reduce this thread count? will
there be any performance impact because of this (our platform experts
suspects so)?

Regards,
Renoy  Paulose

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