Jon Haddad created CASSANDRA-19657:
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Summary: Use more appropriate GC logging
Key: CASSANDRA-19657
URL: https://issues.apache.org/jira/browse/CASSANDRA-19657
Project: Cassandra
Issue Type: Bug
Reporter: Jon Haddad
Our GC default setting spam the gc log resulting in unnecessary IO, cpu usage,
and makes them less effective to use with tools like GCEasy. Here's some
examples of what our defaults log:
{noformat}
[2024-05-22T09:14:45.558-0700][0.022s][11668][9219][trace] Trying to allocate
at address 0x00000006c0000000 heap of size 0x100000000
[2024-05-22T09:14:45.559-0700][0.022s][11668][9219][debug] Running G1 PreTouch
with 4 workers for 4 work units pre-touching 4294967296B.
[2024-05-22T09:23:33.653-0700][121.363s][12868][21251][trace] GC(15) |
255|0x00000007bf000000, 0x00000007bf000000, 0x00000007c0000000| 0%| F| |TAMS
0x00000007bf000000, 0x00000007bf000000| Untracked
[2024-05-22T09:23:33.528-0700][121.238s][12868][21251][trace] GC(15) |
178|0x0000000772000000, 0x0000000773000000, 0x0000000773000000|100%| E|CS|TAMS
0x0000000772000000, 0x0000000772000000| Complete
[2024-05-22T09:24:01.731-0700][149.441s][12868][21251][debug] GC(16) Heap
before GC invocations=16 (full 0): garbage-first heap total 4194304K, used
1918824K [0x00000006c0000000, 0x00000007c0000000)
[2024-05-22T09:24:01.731-0700][149.441s][12868][21251][debug] GC(16) region
size 16384K, 108 young (1769472K), 3 survivors (49152K)
[2024-05-22T09:24:01.731-0700][149.441s][12868][21251][debug] GC(16) Metaspace
used 63070K, capacity 65566K, committed 65680K, reserved 1105920K
[2024-05-22T09:24:01.731-0700][149.441s][12868][21251][debug] GC(16) class
space used 7274K, capacity 8432K, committed 8448K, reserved 1048576K
{noformat}
Quickly looking at the breakdown of trace, debug, and info:
{noformat}
grep trace logs/gc.log | wc -l
7771
grep debug logs/gc.log | wc -l
188
grep info logs/gc.log | wc -l
1065
{noformat}
In summary, we're seeing almost 9K worth of debug and trace log lines for every
1K of INFO, and the debug and trace doesn't have any value for a user that
would leave it unset. Really interested users might want this, but they should
know how to enable it.
We should use the INFO settings by default:
{noformat}
JVM_OPTS="$JVM_OPTS
-Xlog:gc=info:file=${CASSANDRA_LOG_DIR}/gc.log:time,uptime,pid,tid,level:filecount=10,filesize=10485760"
{noformat}
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