Strange bdflush/swap issues
Allen Smith
lazlor at bigboy.lotaris.org
Fri Nov 11 20:26:12 UTC 2005
Running on RHEL3 boxes with 2 processors and 3G of ram. Default bdflush and
elvtune settings.
I am running java apps with big fixed heaps. Total memory used by JVMs and
other system daemons is 2.1G.
These systems run fine during normal use, however once a night I compress old
logs. These logs can be a gig or 2 in size uncompressed. To compress the logs
I use:
'nice gzip -9 filename'
While this gzip is running, my jvms are stopped for periods of time which
causes all kinds of horrible stuff to happen. It looks like the system is
trying to swap out parts of the jvm that aren't active or it is blocking the
few writes to disk that the JVM is doing (logging, async writes).
If I turn swap off, the system performs just fine during this time, no pauses.
What is a good way to track down what is causing this? I think I basically
don't want IO buffer pages to ever push app pages out of ram.
Thanks!
-Allen
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