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From Peter Schuller <>
Subject Re: Nodes frozen in GC
Date Tue, 08 Mar 2011 12:25:04 GMT
> (1) I cannot stress this one enough: Run with -XX:+PrintGC
> -XX:+PrintGCDetails -XX:+PrintGCTimeStamps and collect the output.

Actually, I wonder if it's worth someone getting this enabled by
default, with the obvious problems associated with getting the log
output placed appropriately and rotated. But it really seems to me
like almost every single case of people having problems on the ML:s
would be helped by having instant access to the GC log to rule things
out very quickly and expediently.

I'm not aware of a good simple way to do so though, since the JVM
emits it on stdout (not even stderr) by default, or else to a fixed
file and supports no rotation. Making the file a fifo is possible, but
then one has to have someone reading that file and then that thing
must be monitored, and you introduce the possibility of the log reader
causing JVM hiccups, etc.... does anyone have a good practice for
running production code with GC logging in a way that doesn't interfer
with the normal user who's not actively using it/caring about it?

A related potential mode of backfire is that it might cause blocking
writes to stdout on systems bottlenecking on disk I/O. Maybe it's just
not realistic.

/ Peter Schuller

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