<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Bengt,<div><br></div><div>I also just noticed Bernd's reply as I was drafting this note to you.</div><div><br></div><div>It appears there was a change made possibly after the Java 7 fork. I checked 6u33, (which isn't too old), and got:</div><div><blockquote type="cite"><div><font class="Apple-style-span" color="#000000">$ /home/chunt/jdks/jdk1.6.0_33/bin/java -Xloggc:/tmp/gc.log -XX:+PrintFlagsFinal -version | grep TraceClassUnloading</font></div><div><font class="Apple-style-span" color="#000000"> bool TraceClassUnloading := true {product rw} </font></div><div><font class="Apple-style-span" color="#000000">java version "1.6.0_33"</font></div><div><font class="Apple-style-span" color="#000000">Java(TM) SE Runtime Environment (build 1.6.0_33-b03)</font></div><div><font class="Apple-style-span" color="#000000">Java HotSpot(TM) 64-Bit Server VM (build 20.8-b03, mixed mode)</font></div></blockquote></div><div><div><br></div></div><div>I didn't check any Java 6u* after 33. But, the Java 7 versions I checked shows it disabled with -Xloggc, as you showed with what looks to be a fairly recent HotSpot, or from built directly from hotspot-main's repository.</div><div><br></div><div>Perhaps someone had already noticed this peculiarity previously and the change was integrated into HotSpot after the fork for Java 7? Or, if it's in a 6u* after 6u33, then perhaps it got back ported to Java 6 since 6u33 came after the Java 7 fork.</div><div><br></div><div>Ooh, before I forget ... yeah, I noticed +PrintGC and +PrintGCDetails were auto-enabled with -Xloggc. My question, which I may not have made very clear, was if -Xloggc was auto-enabling +TraceClassUnloading, then why wouldn't it be auto-enabled with +PrintGC or +PrintGCDetails. That's a mute point now since a change has been made to to leave TraceClassUnloading disabled with -Xloggc. ;-)</div><div><br></div><div>Thanks (both you and Bernd) for the additional info and forensics.</div><div><br></div><div>charlie ...</div><div><br><div><div>On Oct 31, 2012, at 10:41 AM, Bengt Rutisson wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div><br>Charlie,<br><br>I don't see any code that enables TraceClassUnloading when -Xloggc is <br>used. Are you sure that this happens?<br><br>When I run it also doesn't look like it gets enabled.<br><br><blockquote type="cite">java -Xloggc:log.txt -XX:+PrintFlagsFinal -version | grep <br></blockquote>TraceClassUnloading<br> bool TraceClassUnloading = false <br>{product rw}<br>java version "1.8.0-ea"<br>Java(TM) SE Runtime Environment (build 1.8.0-ea-b60)<br>Java HotSpot(TM) Client VM (build 25.0-b04, mixed mode)<br><br>We do enable PrintGC and PrintGCDetails when -Xloggc is enabled:<br><br> if (match_option(option, "-Xloggc:", &tail)) {<br> // Redirect GC output to the file. -Xloggc:<filename><br> // ostream_init_log(), when called will use this filename<br> // to initialize a fileStream.<br> _gc_log_filename = strdup(tail);<br> FLAG_SET_CMDLINE(bool, PrintGC, true);<br> FLAG_SET_CMDLINE(bool, PrintGCTimeStamps, true);<br><br> // JNI hooks<br> }<br><br>Bengt<br><br><br>On 2012-10-29 16:06, Charlie Hunt wrote:<br><blockquote type="cite">We stumbled across this last week ... and now curious.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">With -Xloggc, -XX:+TraceClassUnloading is also enabled. But, with other GC related command line options such as; -XX:+PrintGCDetails, -XX:+PrintGC, -XX:+PrintHeapAtGC, etc. -XX:-TraceClassUnloading remains disabled by default.<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">Anyone know the history that led to the decision to only enable +TraceClassUnloading with -Xloggc, and not with say +PrintGCDetails?<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">thanks,<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">charlie ...<br></blockquote><br></div></blockquote></div><br></div></body></html>