-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Chuck,
On 6/22/2010 3:22 PM, Caldarale, Charles R wrote: >> From: Robinson, Eric [mailto:eric.robin...@psmnv.com] >> Subject: Showing Tomcat Memory Utilization with 'top' >> >> 1. Top shows 0k of swap usage, so the system is not swapping. In that >> case, why is there a difference between the VIRT and RES numbers? > > Linux always allocates more virtual space than is actually used (thread stack > space, for example). The JVM will also reserve, but not commit, the -Xmx > size of the heap (and other spaces); it only commits what is really needed. > >> My understanding is that RES=CODE+DATA and VIRT=RES+SWAP. > > Nope. RES is real memory usage, VIRT is just whatever space has been > allocated, but not necessarily touched. Until a page is touched, it won't > exist in RAM or on the swap file. Also, I believe VIRT includes memory shared with other processes, so if you have 50MiB of Java system classes loaded and a modern JVM which shares them among running JVMs, then you'll see that 50MiB included in every process's VIRT that is sharing it, which is somewhat misleading. - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkwhGo0ACgkQ9CaO5/Lv0PCUlwCgmkijMJ5TQN6sMlDAboPU9upV cQEAoI7ZWJaD1hIFsYmx89WnFRjM4dkv =lN9a -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
