> -----Original Message----- > From: Christopher Schultz [mailto:ch...@christopherschultz.net] > Sent: Thursday, May 27, 2010 9:40 AM > To: Tomcat Users List > Subject: Re: tomcat memory question > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > 塗, > > On 5/27/2010 4:51 AM, 塗 wrote: > > there is a problem with my webapp. > > > > web operating environment: > > tomcat5.5.27 + Apache/2.2.3 + jdk1.5.0_13 + Linux_x86_64 > > > > [below] is my manual configurations for tomcat JVM: > > CATALINA_OPTS="-Xms1024M -Xmx1024M > > -Dorg.apache.jasper.compiler.Parser.STRICT_QUOTE_ESCAPING=false" > > Are you using a 64-bit or 32-bit JVM? > > > When my webapp is started, I use the jvm's own tools(jstat) to trace > the > > garbage collections. > > Ok. > > > the Utilization rate of the PC capacity is always 100%. is it > normal? > > What is "PC" (sorry, the jstat man page sucks)? What is the command you > used to produce your jstat output? >
Well, PC is apparently Permanent Capacity in KB, and PU is the current Permanent Utilization (not to be confused with PermGen apparently). Taking his data a sticking it in a spreadsheet (to make it readable) shows that PC is increasing and keeping slightly ahead of PU. I'd say nothing to worry about unless PC is starting to reach PGCMX (which is? Try including the -gccapacity option). Looks like normal GC at work to me. > > Firstly the 1 Full GC is occurrenced within 1 hour, > > 5 hours later that took place within 1 hour 100 Full GC. > > is it normal? > > Can you clarify this last statement? When did the first full GC take > place? When did the second? When did the third? Are you saying that you > get one full GC in one hour, then 5 hours for the second, then 100 full > GCs all close together? > The OPs original statement makes no sense in light of the data give. There is no Full GC count line in his data (though doc says there should be: http://java.sun.com/j2se/1.5.0/docs/tooldocs/share/jstat.html). The doc seems to imply that the GC times should be cumulative from start, so it looks like he's done some Full GC between each sample taken (about 7 secs/hr.) It would be really helpful if he had listed his jstat options. All the actual capacity/utilization numbers appear to be rising and falling over time in apparent relation to normal usage. The permanent util number doesn't seem to drop often, so he may have a memory leak. (I'd seek the opinion of someone more versed than me in reading jstat output though.) It would have been useful if he had a specific issue he was having and trying to resolve. > That suggests to me that your webapp is allocating memory and never > releasing it. This could be due to many reasons such as a memory leak > (which ought to be fixed) or caching (which may be working as > designed). > > Is your webapp performing well? GC activity doesn't necessarily mean > that anything is wrong. > > - -chris > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.10 (MingW32) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iEYEARECAAYFAkv+hFoACgkQ9CaO5/Lv0PBFkgCgvqoksV7PgaqGFOI5wCgXwaIa > yKcAniKySqd3g8wd7paAoRBn0mWklSZY > =RfE/ > -----END PGP SIGNATURE----- > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > ******************************* NOTICE ********************************* This message is intended for the use of the individual or entity to which it is addressed and may contain information that is privileged, confidential, and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by reply or by telephone (call us collect at 512-343-9100) and immediately delete this message and all its attachments.
