Re: Memory usage with multiple instances of tomcat
Thank you Chuck and Chris for your help and advice. I will definitely be reading your refs Chris Regards Peter - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Memory usage with multiple instances of tomcat
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Peter, > 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3 > instance use 6 GB between them ? Each instance gets a separate, 2GB heap space. > 2. or do they potentially share they same memory? Since Java 1.5, "shared archive" capability is available on Sun's JVM. This basically means that the core JVM stuff can be memory-mapped and thus shared between processes, so you actually get a benefit when you run multiple simultaneous JVMs. See: http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html#vm_classdatashare http://java.sun.com/j2se/1.5.0/docs/guide/vm/class-data-sharing.html These pages cover this capability if you re interested in reading all about it. - -chris -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.7 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGt1nW9CaO5/Lv0PARAlFHAJ4q/MBMWrYMUBJTeu3/RPyzU1b1AQCfe8SJ AMWfHzrgP0dAKeifLPxQ4Bw= =5Dw/ -END PGP SIGNATURE- - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: Memory usage with multiple instances of tomcat
> From: Peter Sparkes [mailto:[EMAIL PROTECTED] > Subject: Re: Memory usage with multiple instances of tomcat > > The commands -Xms3g -Xmx3g will set the min/max heap to > 3 GB, please how do I set the RAM for each instance of > Tomcat5.5 to 2 GB You can't set the amount of RAM for any process - the OS decides which processes get how much RAM out of the total available. Unfortunately, Linux isn't particularly good at optimizing paging, so you're best to keep the aggregate of virtual space allocations under the total RAM. With three instances of Tomcat running, each with 3 GB heaps, you run the risk of excessive paging if all the heaps get close to full at the same time. You might want to reduce the -Xms and -Xmx settings to something like 2512m. - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Memory usage with multiple instances of tomcat
Thanks Chuck, I am using a 64-bit versions of the OS and JVM and I was confusing virtual memory with RAM. I have 8 GB of RAM and a 80 GB disc. The commands -Xms3g -Xmx3g will set the min/max heap to 3 GB,please how do I set the RAM for each instance of Tomcat5.5 to 2 GB Regards Peter From: Peter Sparkes [mailto:[EMAIL PROTECTED] Subject: Memory usage with multiple instances of tomcat 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3 instance use 6 GB between them ? 2. or do they potentially share they same memory? Don't confuse virtual memory with RAM. The heap allocations are virtual, so there is no physical relationship with the amount of RAM you have. (There are performance considerations, of course, in that if you significantly oversubscribe RAM, you may suffer from excessive paging.) One thing you've failed to mention is whether you're using 32- or 64-bit versions of the OS and JVM. If 32-bit, then process virtual space is typically limited to 2 GB, and the heap, code, and supporting libraries must fit within that - you won't be able to allocate all 2 GB to the heap. If you're running a 64-bit environment, the sky's the limit (almost), and you could make each heap 256 GB, even with only 8 GB of RAM (not recommended, due to aforementioned paging concerns). Since each Tomcat runs as a separate process, there is no active sharing of either heap or code across instances. However, if you're running a client version of a current HotSpot JVM, there is some sharing of loaded classes in the PermGen (other than static fields), primarily to reduce startup time. You can see the shared amount in the Memory tab of JConsole. There is not currently any sharing in the server version of the HotSpot JVM. - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: Memory usage with multiple instances of tomcat
> From: Peter Sparkes [mailto:[EMAIL PROTECTED] > Subject: Memory usage with multiple instances of tomcat > > 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3 > instance use 6 GB between them ? > 2. or do they potentially share they same memory? Don't confuse virtual memory with RAM. The heap allocations are virtual, so there is no physical relationship with the amount of RAM you have. (There are performance considerations, of course, in that if you significantly oversubscribe RAM, you may suffer from excessive paging.) One thing you've failed to mention is whether you're using 32- or 64-bit versions of the OS and JVM. If 32-bit, then process virtual space is typically limited to 2 GB, and the heap, code, and supporting libraries must fit within that - you won't be able to allocate all 2 GB to the heap. If you're running a 64-bit environment, the sky's the limit (almost), and you could make each heap 256 GB, even with only 8 GB of RAM (not recommended, due to aforementioned paging concerns). Since each Tomcat runs as a separate process, there is no active sharing of either heap or code across instances. However, if you're running a client version of a current HotSpot JVM, there is some sharing of loaded classes in the PermGen (other than static fields), primarily to reduce startup time. You can see the shared amount in the Memory tab of JConsole. There is not currently any sharing in the server version of the HotSpot JVM. - Chuck THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY MATERIAL and is thus for use only by the intended recipient. If you received this in error, please contact the sender and delete the e-mail and its attachments from all computers. - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Memory usage with multiple instances of tomcat
Thanks Adrian Regards Peter You'll need to allocate 2GB to each Tomcat instance. As long as you use the standard Tomcat startup scripts each Tomcat instance will run in a separate JVM (you'd have to be pretty deliberate about making it run any other way). Regards, Adrian Sutton http://www.symphonious.net On 04/08/2007, at 4:16 PM, Peter Sparkes wrote: Hi, I followed the "Tomcat with 8 GB memory" thread but did not find the answer to the following question: I am setting up a Linux server with 8 GB memory which will be running 3 instances of tomcat 5,5; when I allocate memory to java, say 2GB: 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3 instance use 6 GB between them ? 2. or do they potentially share they same memory? In other words with the 6GB I want to share between the 3 separate Tomcat instances do I allocate the whole 6GB to Java or 2GB Thank you Peter Sparkes - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: Memory usage with multiple instances of tomcat
You'll need to allocate 2GB to each Tomcat instance. As long as you use the standard Tomcat startup scripts each Tomcat instance will run in a separate JVM (you'd have to be pretty deliberate about making it run any other way). Regards, Adrian Sutton http://www.symphonious.net On 04/08/2007, at 4:16 PM, Peter Sparkes wrote: Hi, I followed the "Tomcat with 8 GB memory" thread but did not find the answer to the following question: I am setting up a Linux server with 8 GB memory which will be running 3 instances of tomcat 5,5; when I allocate memory to java, say 2GB: 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3 instance use 6 GB between them ? 2. or do they potentially share they same memory? In other words with the 6GB I want to share between the 3 separate Tomcat instances do I allocate the whole 6GB to Java or 2GB Thank you Peter Sparkes - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Memory usage with multiple instances of tomcat
Hi, I followed the "Tomcat with 8 GB memory" thread but did not find the answer to the following question: I am setting up a Linux server with 8 GB memory which will be running 3 instances of tomcat 5,5; when I allocate memory to java, say 2GB: 1. Does each tomcat instance use a separate 2 GB of memory, ie the 3 instance use 6 GB between them ? 2. or do they potentially share they same memory? In other words with the 6GB I want to share between the 3 separate Tomcat instances do I allocate the whole 6GB to Java or 2GB Thank you Peter Sparkes - To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]